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The search for an understanding of evolutionary processes affects all biologists, yet, despite our confidence in the scientific method, we are really no closer to an explanation than were the philosophers of natural history prior to the publication of Tuatara is devoted to Croizat and an assessment of his work by
Croizat does not conform to our view of a typical biological research worker and, not surprisingly, he has come up with original, nonconformist ideas about the history of life on earth. Some relevant biographical notes have been provided by Principia Botanica(pp. 26-48). The concept of this issue was being discussed with Croizat's before his death in November 1982, by which time he had submitted a manuscript to Tuatara. In this posthumous paper (pp. 49-68) Croizat conveys his frustration over the manner in which his work has been received and misinterpreted by Ernst Mayr. The manuscript has been condensed somewhat by
The enthusiasm of the three New Zealand contributors toward their self-appointed tasks knew no bounds and made overall editing very straightforward. My thanks to them.
Present Address: Entomology Division, D.S.I.R., Private Bag, Auckland, New Zealand.
A brief biography of
Keywords: biogeography, botany, Coro, Croizat, evolution, Harvard University, Italy, Venezuela.
From an early age Croizat enthusiastically studied living nature, in both the wild and under captivity/cultivation. He was privileged to know the wealthy, elderly count Mario Peracca who was an eminent herpetologist. The young Croizat was often a guest of Peracca and spent many hours in his greenhouse through which Galapagos tortoises and giant iguanas roamed freely.
University studies were interrupted by the First World War, during which Croizat served in the Italian Army from 1914 to 1919, attaining the the rank of infantry captain. In 1920 he received his law degree from the University of Turin, and commenced work in a textile mill, which a friend owned.
During the war Croizat had married. A son Victor was born in 1919, and was followed by a daughter Georgette in 1921. By this time the oppressive Fascist political movement led by Mussolini was rapidly gaining power in Italy. Naturally Croizat actively opposed Fascism, but in the face of threats was forced to leave Italy. Like many others at this time he chose to emigrate to the United States.
Early in 1923 the Croizat family landed in New York, and thus began long years of hardship and poverty. Croizat was forced to seek menial employment at the lowest possible wages. Seeking refuge from the drudgery of his daily routine, he developed an interest in water colour painting. By 1929 he was achieving some success in this field and exhibited paintings at the Brooklyn Museum of Art, to which he sold one for the then not inconsiderable sum of S100. The Wall Street Crash of 1929/30 destroyed the American market for contemporary art works, and Croizat decided to further his artistic career in Paris.
Arriving in Paris, Croizat found it impossible to succeed as an artist primarily because of the extremely corrupt nature of the Parisian art
“I entered my new job in 1937…and began to publish which promptly involved me in difficulties on account of the censorship I was supposed to accept, but I would not recognize. Merrill kept me on, nevertheless, as a consultant on matters of languages (I can freely handle French, Italian, Spanish, Portuguese, Latin, Russian, German and with a dictionary Greek…) and morphology, etc. This left me free of my time, and I readily conceived the project of effecting the broadest possible survey of the international streams of botanical thinking from the days of Caesalpin to the present.”
As a result of this reading Croizat accumulated three to four hundred booklets of notes, which later formed a reference base for his books and many of his papers. But he was not only a student of botanical literature. He firmly believed in testing both the writings of others and his own observations in the herbarium, whenever possible, against the study of living plants. An eminent American botanist, who knew Croizat at Harvard, writes of his skills as a botanist thus:
“Croizat was working on the Euphorbiaceae while here and his drawings, dissections, annotations on herbarium sheets are superb…Croizat's notes on the genus
Crotonin our herbarium remain for who ever tackles that difficult group and no one has been willing to do so. He saw types in Europe and made comparisons from memory and several I have checked up on are accurate to an unbelievable degree.”
Unfortunately, Merrill was levered from his directorship of the Arboretum in 1946, and Croizat was dismissed only a few months short of tenure. Instrumental in Croizat's dismissal appears to be the fact that he had written a paper on Trochodendron and Tetracentron that was critical of several studies on the same two genera published by Journal of the Arnold Arboretum but Bailey prevented publication. Eventually Croizat's paper appeared in the equally reputable journal Bulletin of the Torrey Botanical Club.
Unable to find another post in the United States, Croizat obtained a scientific job in Caracas, Venezuela. From 1947-1952 Croizat held a number of academic positions in Venezuela, and in 1950-1951 was botanist on the Franco-Venezuelan Expedition to the sources of the Orinoco River. At this time he was divorced from his first wife and married his second wife. In 1953 Croizat, encouraged by his new wife, gave up official academic positions to work full time on biological problems.
His first book Manual of Phytogeography was written by the time he landed in Venezuela, and this was published by the prestigious Dutch firm, Junk of the Hague. In Croizat's own words the rest of his work “came out of a most unpretentious near-shack of two rooms and a kitchen in the point of Caracas know as Chapllin a Country Club, which was home to us from 1953-1975, with two interruptions: in 1959-1960 a fast trip (to) South America…, and in 1962-1963 to Europe…where I spoke in the hall of the Linnaean Society of London and in the Musée d′ Histoire Naturelle of Paris”.
In 1976, Croizat (aged 82!) and his wife took over as first Directors of the “Jardin Botanico Xerofito” in Coro, a city about 300 miles west of Caracas'; a botanical garden which they founded and had worked hard to establish since 1970. Incidentally, the gardens are now to be named after Croizat. This happy occasion was marred by Croizat losing his right eye in February, 1976. Further ill-health followed and culminated in a major abdominal operation in May, 1979. By now old age had taken its toll. The fact that the paper in this volume was written and typed out in August, 1982 by an 88 year old, (blind in one eye and with the use of only one hand), three months before his death, testifies not only to the lucidity of Croizat's thought but also to the vigour with which he fought academic authority and learned ignorance.
Croizat died on November 30, 1982 of a heart attack. I can find no better epitaph than a few lines he wrote me in April, 1982:
“I have indeed lived and worked to my taste either in art or science. What more could a man desire? Knowledge has always been my goal. There is much that I shall leave behind undone…but something at least I was privileged to leave for the world to use, if it so intends.…As the Latin poet said I will leave the table of the living like a guest who has eaten his fill. Yes, if I had another life to spend, I certainly would not waste it. But that cannot be, so why complain?”
No published account of Croizat's life has so far appeared, apart from very concise autobiographical notes at the end of Croizat (1982). In his scientific work, Croizat made occasional allusions to incidents in his life. For instance, readers familiar with Volume Ib of Principia Botanica(p.p. 1299-1300) will already be aware of Croizat's opposition to Fascism. The chief source upon which I have based this account is a series of letters, concerning his life, that Croizat wrote at my request in March and April, 1982. I have supplemented these detailed accounts with material (personal correspondence and a tape interview with Croizat) generously supplied by Gareth Nelson, American Museum of Natural History.
Present Address: Entomology Division, D.S.I.R., Private Bag, Auckland, New Zealand.
Leon Croizat 's bold and novel attemps to empirically refuteCharles Darwin 's theory of geographical distribution of organisms by their “means of dispersal”, A. R. Wallace's classification of zoogeographic regions, and Alfred Wegener's concept of Pangaea are discussed. Croizat's panbiogeographic methodology and synthesis, an alternative approach to these generally accepted views, is discussed in relation to vicariance cladistic biogeography with which it is often confused.
Keywords: biogeography, cladistics, Croizat, Darwin, dispersal, geology, pan-biogeography, vicariance, Wallace, Wegener.
“It may be said, indeed, that Darwinianism, Workmen and Work, Edinburgh, T. & T. Clark). Stirling's critique is philosophical, and heavily coloured by an abstruse Hegelianism, but it is nevertheless perceptive in that it strikes straight at the major weakness of Darwin's theory of evolution by natural selection: the notion that the differentiation of organisms in space and time is a consquence of their originating in specific centres of origin from whence they migrate by means of dispersal, thus to establish their geographic distribution. Darwin's world is a world where organisms are constantly moving, continually pouring forth from specific evolutionary centres that supply advanced and more competitive organisms to other areas of the globe.
There have been many critiques of Darwinism, both before, and after the publication of Stirling's work. Most, if not all, of these critiques focus upon the problem of form initially, and argue that natural selection, as conceived by Darwin cannot possibly account for the origin of new structural types of animals and plants. These critiques range from the superb to the indifferent. Some of these critiques like St. George Mivart's On the Genesis of Species, will never be surpassed. But only
Croizat's criticism of Darwinism is the most fascinating ever published, because he chose not to address himself primarly to the problem of form, but rather to the problem of space. For it is through space and in time that the forms of organisms change. Darwin too, of course, thought that biogeography was an interesting subject, for otherwise he would not have introduced “On the Origin of Species” to the world through the medium of this discipline:
“When on board H.M.S.
Beagleas naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America…” (Introduction to“On the Origin of Species”).
And this is Croizat's very point; Darwin knew the importance of the spatial aspect, but failed to capitalise on his initial insights into the problem as recorded in The Voyage of the Beagle when he came to write The Origin (see Croizat, 1964: Space, Time, Form, pp. 592-641).
Croizat thought of doing something that no one had ever thought of doing before, and that no one will probably ever do again. He decided to subject Darwin's theories to an empirical test and posed the question: “Did the geographical distribution of organisms in space and through time, by form support the Darwinian view that means of dispersal, and migrations by these means out of specific centres of origin was the process responsible for geographic distribution?” In order to undertake this massive and challenging experiment Croizat developed his track method of investigation, which enabled him to analyse the geographic distributions of organisms and graph them into what he termed dispersal patterns.
Croizat found that these dispersal patterns were rather repetitous, and that apparently highly vagile organisms like birds and butterflies exhibited very similar dispersal patterns to extremely sedentary organisms, with no obvious means of dispersal, such as earthworms and flightless beetles. He discovered that these repetitious patterns, which he termed standard or generalised tracks, bore no relationship to the present day geography of the world, but rather joined areas of the globe that were widely separated; for instance one of his standard tracks crossed the Tasman Sea from New Zealand to Southern Australia/Tasmania, and then drove straight on out over the vast expanse of the Indian Ocean to Southern Africa, while another headed in the opposite direction from New Zealand over the Pacific Ocean to Western South and North America. Various standard tracks were found to overlap with considerable complexity in areas of endemism like New Zealand, and Croizat considered this a major problem of biogeography (Fig. 1).
Of course, the Darwinian answer to this complex pattern of biogeo-graphic area relationships is that present day biota, such as that of New Zealand, have extremely diverse relationships because the means of dispersal of organisms are responsible for the presence or absence of a particular organism in the biota. Each group of organisms in the biota has had a history unique to itself. Biogeography is just telling a ‘story’: unique narrative explanations are proposed for the historical development of each group studied. But using this approach one can explain everything and anything, and faced by anomalies like organisms with no obvious means of dispersal living on isolated islands, Darwinian biogeographers attribute their presence there to “chance”. In contrast to this approach, Croizat suggested that many parts of the world have complex biogeographic relationships because they are biogeographic boundaries.
Because they are biogeographic boundaries, they were also to Croizat geological boundaries. This novel concept brought Croizat into conflict with the view, (originating in the 19th century in the works of de Candolle, Sclater, Wallace, and others), that present day landmasses could be classified and divided up into some coherent system of phytogeographic and zoogeographic regions, provinces and areas of endemism. Naturally, this latter view found much support from the geological conception of the permanence of continents and oceans, which was especially prevalent in the 1940s and 1950s when Croizat did most of his work. Some commentators (e.g. Nelson in Vicariance Biogeography: a critique) have argued that “the revival of continental drift during the 1960s was the doom of Wallace's synthesis”. But as Mayr (The Growth of Biological Thought) has recently argued “the major landmasses (plates) are still considered permanent, their positions and connections are changing in the course of time”. Mayr ingeniously rescues the Wallacean position of the permanence of continents, through his appeal to continental drift, and its attendant
To Croizat though, the concept of Pangaea was wrong because it conflicted with evidence he had obtained from his purely biogeographic studies. The continents are not permanent, he repeatedly stated: one cannot pull them all back into a single supercontinent as Wegener did, and modern plate tectonic proponents do. Very recently geologists have begun to unearth evidence (review in JI. Geophys. Res. 87:3644-3661) that most, if not all, of the world's continental landmasses are not permanent and stable, but rather composite formations that have been formed by the accretion of crustal blocks since the Permian. The geological and geophysical findings of the 1980s promise to corrobrate Croizat's biogeographic work, in novel and exciting ways.
The regions, subregions, areas of endemism, etc., of de Candollean phytogeography and Wallacean zoogeography, based on the idea of the permanence of continents and other landmasses, are thus not parts of the real, natural world to Croizat (Fig. 2). But what is needed to demonstrate that the “unproblematical” areas of endemism of Nelson and Platnick
Systematics and Biogeography: Cladistics and Vicariance) are not natural biogeographic taxa is the equivalent of a concept of homology in biogeography.
In his study of epistemological ruptures in Western thought, The Order of Things), argues that scientific animal and plant systematics did not exist in the 18th century. Foucault locates the essential discontinuity in the history of biological systematics between Linnaeus and Cuvier:
“…Cuvier.…introduced a radical discontinuity into the Classical scale of beings; and by that very fact he gave rise to such notions…that make possible…the idea of evolution.…With spatial discontinuity, the breaking up of the great table, and the fragmentation of the surface upon which all natural beings had taken their ordered places, it became possible, to replace natural history with a ‘history’ of nature. It is true that the Classical space…did not exclude the possibility of development, but that development did no more than provide a means of traversing the discreetly preordained table of possible variations. The breaking up of that space made it possible to reveal a historicity proper to life itself…” (p. 275)
That historicity, the breaking up of the organism, that analysis; the becoming of animal and plant systematics as a science is a direct consequence of the development of a concept of homology, particularly in the work of Cuvier's disciple
Analogously, this is a major thrust in Croizat's work, from the very opening pages of his first biogeographical book Manual of Phytogeo-graphy, all though his subsequent work, Croizat relentlessly and frenetically pursues the question: “What is the equivalent of a concept of homology in biogeography?” Is it means of dispersal, dispersal routes and centres of origin as in Darwinian and Wallacean biogeography? Is it endemic taxa and their relationships, that define areas of endemism and their relationships, as in vicariance biogeography? Or is it something else again, something no one ever thought of until Croizat? To Syst. Zool. 32: 431-438 for further discussion.)
Naturally, an epistemological break (i.e. rupture or discontinuity with past thought in a discipline) of this magnitude inevitably leads to a polemical and provocative confrontation for a 150 year old tradition of de Candollean and Darwinian orthodoxy in biogeography is not lightly challenged:
“I have no wish to oppose academic notions of ‘means of dispersal’ because I dislike what some say of it at this hour. I intend to destroy these notions because they positively interfere with the advance of knowledge on far-reaching points of evolution over space, in time, by form” (Croizat,
Space, Time, Form, p. vi)
while:
“It is of course well known that the time-honoured pastime of rigging up ever better ‘zoogeographic’ provinces or the like has no end because,…life perversely tends to interdigiage all over, thus voiding man's clever schemes” (Croizat,
Panbiogeography, Vol. 2a: 131).
Croizat's work is popularly, but erroneously, associated with the New York school of vicariance cladistic biogeography, developed by workers such as Nelson's, Rosen and Platnick. In fact, shortly before his death
Systematics and Biogeography was uncompromising in his opposition to vicariance biogeography:
“Croizat has…worked hard and long to rid biogeography of the ‘definitive authority’ of Simpson, Mayr, Darlington, etc., and is now working, because of the very same reasons, against the ‘authority’ of Nelson and his acolytes. Croizat offers no ‘authority’, just a method of positive investigation—the panbiogeography.”
True Croizat's style is lively and vigorous, and ruthlessly uncompromising in criticism of those with whom he disagreed. For these very human errors he has been much criticized by those for whom science is an occupation rather than a passion. It is because his books are intense and ardent conversations on the development of methods for investigating biogeographic and systematic problems that they will live. Pan-biogeographic methodology and synthesis is here to stay.
A concept of internally directed evolution is recognised in Croizat's pan-biogeographic synthesis as being fundamental to an understanding of the evolutionary process. The meaning and application of Croizat's concept (orthogeny) is briefly discussed. Reference is made to similar concepts by other biologists, in particular the “laws of growth” by
Charles Darwin . Contrast is made between the primary role of orthogenesis attributed by Croizat, and the viewpoints of contemporary evolutionary thought.
Keywords: adaptation, Croizat, Darwin, natural selection, orthogeny.
An exciting aspect of Croizat's “panbiogeography” is that the formerly disparate disciplines of biogeography and evolution become integrated within the framework of a single general synthesis. This synthesis recognises evolution as the interaction of “space, time and form” and Croizat summarises the concept of evolution by the formula: Evolution equals space + time + form. In contrast, orthodox evolutionary studies concentrate on form (over time) and this is reflected in the definitions given by Eldredge (1979) of “descent with modification” and “change in gene frequencies”.
Croizat's unique approach to evolution is to use biogeographic analysis as the basis for understanding the process responsible for change in form through time and over space. This analysis has furbished concepts that lead not only to a re-evaluation of Darwin's understanding of dispersal but also the role of natural selection as the primary mechanism of change. Although not the first to question the power of natural selection, Croizat discusses extensively the concept and role of another evolutionary process called “orthogeny” and investigates its relationship to adaptation and other aspects of organic evolution.
The orthodox evolutionary framework recognises directionality (or trend) in evolution but attributes this to natural selection (Stebbins 1967,139; Dobzhansky 1970,391; Dobzhansky et al. 1977,120; Mayr 1978,47; Gould 1982,381; Campbell 1982,192). However there exist in nature, “types of organisation” (recognisable “structural” groups) to which the member organisms are seen to conform, regardless of their environment or manner of adaptation. This shows that despite variation in environment acting on an organisim through natural selection, the form of the organism is already determined according to the type of organisation inherited. This process of non-environmental determination is therefore a set of inherent tendencies which “orient” evolution regardless of environment. This is the process Croizat (1964,678) refers to as “orthogeny”. By way of example, a scorpion “adapted” to the desert is a “scorpion” rather than the type of organisation of similarly “adapted” organisms such as a “tortoise” or a “camel”.
Apart form “orthogeny” a variety of terms have been used in reference to internally directed evolution or inherent tendencies, including “orthogenesis” (first used by William Haake in 1893 and later adopted by Eimer 1898,19); “nomogenesis” (Berg 1926); “germinal stream” (Metcalf 1928); and “internal factors” (Whyte 1963, Grasse 1977). Less explicit reference has been made by other biologists using terms such as “oriented evolution” (Simpson 1960); “nature of the organism” (Dobzansky 1960,407); and “historical burden” (Wiley & Brooks 1982). Athough
Although well known for the evolutionary synthesis “Origin of Species by Natural Selection” Darwin also attributed evolution to directional factors independent of the environment which he repeatedly referred to as “laws of growth”. Some of these statements are reproduced elsewhere in this issue. Darwin's reference to laws of growth is important because it shows that just as Darwin knew of vicariant form making (Croizat 1964;621) he was also aware of orthogeny, Vicariant form making is a fundamental aspect of dispersal (and therefore evolution in general). During evolution different forms evolve in different localities so they replace each other over space to form a mosaic pattern (Croizat 1961,1454). Examples and the implications of vicariism are discussed extensively throughout Croizat's work. However vicariism was subsumed by Darwin under “centres of origin” and “means of dispersal” while orthogeny was neglected in favour of “natural selection” in his general synthesis.
The essence of what Darwin (1860,205) had to say was that although we may be ignorant of the nature of many features, evolution by orthogeny could be regarded as the origin of many structures and this did not require immediate usefulness or advantage. Even though Darwin's evolutionary synthesis favoured the role of natural selection, he expressed some doubt (Darwin and Seaward 1903) over this decision and believed that there was much yet to be learned about “laws of growth”. Darwin (1888,61) clearly indicated that natural selection came to work on what laws of growth (orthogeny) provided. Because of this Croizat (1964,657) notes that while some might rank Darwin as an “orthogenist” others would deny this, and suggested that Darwin himself may not have been able to resolve the question. Darwin was certainly aware of more than one agent of change, this apparently being the basis of Gould and Lewontin's (1979) description of “pluralistic” to Darwin's approach of identifying the agents of evolutionary change. However “pluralistic” falls far short of “synthesis” and while Darwin was pluralistic in recognising the existence of vicariism and orthogeny, he failed to underscore their relative importance in evolution. This failure set the pattern for much of biogeography and evolution to this date.
Apart from Croizat, substantial discussion of orthogeny includes Eimer (1898) (Eimer's ideas are discussed in some detail by Bowler 1979), Berg (1926), Metcalf (1928), Trueman (1940), and Whyte (1965). (Whyte's background is primarily with physics and the philosophy of science and apparently he was not aware of Croizat's work). Orthogeny also formed the basis for Rosa's theory of holpgenesis (Rosa 1923, IB). Much smaller contributions are given by other biologists such as Grasse (1977) and Riedl (1978). The major irony of post-Darwinian orthodoxy is that while orthogeny was explicitly ignored or condemned, the very same biologists when faced with the facts, resorted to descriptions that were of an orthogenetic content. Examples are Simpson (Croizat 1964, 622-644), Huxley and Mayr (Brundin 1968, 487-493).
The mainstream of orthodoxy, exemplified by Darwinism and neo-Darwinism, placed orthogeny as unscientific. Mayr (1978,42) claimed that those who reject natural selection and put forward the alternative of orthogeny, “relied on some inbuilt tendency, drive toward perfection or
Orthogeny in the sense of Darwin, Berg, Croizat, Whyte, etc (and see Rosa 1923,124) is not at all mysterious or teleological. Change in form is merely a consequence of the initial state, followed by evolution according to laws and potential. It is of interest to note in reference to Mayr's (1978) denouncement of orthogeny because of teleology, that orthodox evolutionary views of adaptation involve explaining the origin of a structure in terms of ends and can therefore be described as teleological (e.g. Dobzhansky 1970, 4; Ruse 1982).
Some biologists have referred to orthogeny in terms of a pattern of linear series or trends, often in reference to the fossil record (Shull 1936, Simpson 1960, Eaton 1970, Avers 1974, Dobzhansky et al. 1977, Mayr 1978, Stanley 1979, Minkoff 1983). In this context, “examples” of orthogeny are criticised for failing to conform to an arbitrary requirement for some sort of linearity or undeviating constancy. Such an approach has obscured the primary concept of orthogeny as a process involving inherent tendencies, and determinant change (cf Trueman 1940,87). Also ignored is the role of dispersal (evolution through space and time) whereby characters displayed in the ancestor become differentially represented in the descendants (Croizat 1961,1566). The recombination may sometimes produce varied and novel forms, but they remain within the possibilities determined by the particular orthogeny.
Orthogeny is an important concept in biology because the implications of such a process for understanding the relationship of plants and animals with the environment, are radically different to that provided by the orthodox evolutionary framework. Lewontin (1982) claims that internal and external processes are equal and there is a “coevolution” between the two. However, Croizat (1964,683) points out that with orthogeny dertermining the type and range of variation natural selection can at best have only a secondary role because it cannot act beyond the variation provided. Berg (1926) believed that natural selection could have no evolutionary role at all.
Natural selection as the main creative mechanism of evolution is considered by Toumi (1981) and Gould (1982,380) to be a central part of Darwinism. According to Mayr (1982,165) long term evolution is inconceivable without natural selection. Eldredge and Gould (1974) went so far as to exclaim, “surely we ‘believe’ in regimes of natural selection which affect a transformation of the gene frequency of populations, in a regular and progressive manner. How else can we explain adaptation?” Lewontin (1978) believed “adaptation” to be sometimes hard to define and described the “modern” view of adaptation as “problems set by the environment which organisms need to solve”. Gould (1982,383) admitted that the
“the constraints of inherited form and developmental pathways may so channel any change, even though selection induces motion down permitted paths, the channel itself represents the primary determinant of evolutionary direction.”
At the risk of misconstruing Gould's arguments it would seem that they come as close to orthogeny as possible without admitting it and Gould (1977,85; 1982,383) only avoids this by claiming that the channels may be set by past adaptations so selection remains pre-eminent. However, with orthogeny this “pre-eminence” is not possible. Because Gould and Lewontin (1979,593) believe orthogeny must be rejected as a “close appeal to mysticism”, they claim (p594) that change in structural organisation “may” be mediated by natural selection and yet they believe that constraints become “much the most interesting” aspect of evolution! The “pluralism” of Gould and Lewontin appears to provide no more synthesis than Darwin over 150 years ago. The only biologist to attack this crippling confusion at its roots is Croizat.
In contrast to Gould's contradictive manoeuvering between “constraints” and “natural selection”, the process of adaptation by orthogeny is much more straightforward. Natural selection can only be secondary to orthogeny and so interpretation of adaptation must look first to structure, not the resulting function. Adaptation is seen as the result of 2 distinct components, “structural adaptation” which is primary and orthogenetic, and “environmental adaptation” which is secondary and mediated by natural selection (Croizat 1964, 709). This understanding of adaptation does not rely on guessing the original relationship to be “advantageous”, “selective”, “non-adapative”, “neutral”, “preadaptive”, etc. Gould and Vrba (1982) argue for a missing concept in evolution which they call “exaptation” so to encompass the evolution of features not due to present utility. However the missing concept is not exaptation but orthogeny which eliminates the “problems” experienced by Gould and Vrba (1982).
The underlying mechanism of orthogeny is identified by Croizat (1964,680) as a prime goal of evolutionary research. The main concern of evolutionary genetics has been with natural selection and the relationship of environment to gene frequency and expression (Dobzhansky 1970, Berry 1982). A concept of orthogeny calls for re-evaluation of genetic interpretation, including the nature and role of mutation. In its genetic aspect, biological study has not yet generated a comprehensive understanding of orthogenetic processes. Although Dobzhansky et al. (1977,77) claimed “the birth of molecular genetics has finally disposed of any the oretical basis for internally directed orthogenetic evolutionary trends”, the mechanism of “molecular drive” proposed by Dover (1982) gives explicit recognition to a possible directional quality in evolution. (See also Campbell 1982, Hunkapiller et al. 1982).
It has been stated in the analysis of Darwinian evolutionary study by Hull (1974,120) that:
“Future biologists may produce new biological theories, perhaps new versions of evolutionary theory, that make no reference to organisms, or the reproductive relationship between them…the conceptual revolution necessary for such a change would be enormous”.
The concepts of dispersal and orthogeny introduced by Croizat, in a comprehensive evolutionary synthesis involving space, time, and form, clearly indicate that such a revolution in biology has already begun.
Although
Charles Darwin is credited with having recognized natural selection as the fundamental process accounting for the evolutionary change and adaptation of organisms, it is not generally recognized that this is not Darwin's true position. A series of quotations from Darwin's books and his posthumously published letters are presented. These illustrate that on a number of occasions Darwin recognized “laws of growth” as being a more important evolutionary process than natural selection.
Keywords: Darwin, evolutionary processes, laws of growth, natural selection.
1. 1860: “On the Origin of Species by means of natural selection”, 5th thousand.
p. 205: “We are far too ignorant, in almost every case, to be enabled to assert that any part or organ is so unimportant for the welfare of a species, that modifications in its structure could not have been slowly accumulated by means of natural selection. But we may confidently believe that many modificatious, wholly due to laws of growth, and at first in no way advantageous to a species, have been subsequently taken advantage of by the still further modified descendants of this species.”
2. 1872: “On the Origin of Species by means of natural selection”. 6th Edition.
p. 157-158: “… we may easily err in attributing importance to characters, and in believing that they have been developed through natural selection. We must by no means overlook the effects… of the complex laws of growth, such as correlation, compensation, of the pressure of one part on another.… But structures thus indirectly gained, although at first of no advantage to a species, may subsequently have been taken advantage of by modified descendants, under new conditions of life and newly acquired habits.”
p. 173: “Now although natural selection may well have had the power to prevent some of the flowers from expanding, and to reduce the amount of pollen, when rendered by the closure of the flowers superflous, yet hardly any of the above special modifications can have been thus determined, but must have followed from the laws of growth, including the functional inactivitiy of parts, during the progress of the reduction of the pollen and the closure of the flowers.
It is so necessary to appreciate the important effects of the laws of growth…”
p. 174: “In numerous other cases we find modifications of structure, which are considered by botanists to be generally of a highly important nature, affecting only some of the flowers on the same plant, or occurring on distinct plants, which grow close together under the same conditions. As these variations seem of no special use to the plants, they cannot have been influenced by natural selection.”
p. 175: “We thus see that with plants many morphological changes may be attributed to the laws of growth and the interaction of parts, independently of natural selection.”
3. 1903: More letters of
p. 144-145: “…do you really suppose that for instance Diatomaceae were created beautiful that man, after millions of generations, should admire them through the microscope? I should attribute most of such structures to quite unknown laws of growth;… When any structure is of use…, I can see with my prejudiced eyes no limit to the perfection of the coadaptations which could be effected by Natural Selection.”
4. 1903: More letters of
p. 343: “I should be inclined to attribute the character in both your cases to the laws of growth and descent, secondarily to Natural Selection. It has been an error on my part, and a misfortune to me, that I did not largely discuss what I mean by laws of growth at an early period in some of my books. I have said something on this head in two new chapters in the last edition of the
Origin.…Endless other changes of structure in successive species may, I believe be accounted for by various complex laws of growth. Now, any change of character thus induced with advancing years in the individual might easily be inherited at an earlier age than that at which it first supervened, and thus become characteristic of the mature species; or again, such changes would be apt to follow from variation, independently of inheritance, under proper conditions. Therefore I should expect that characters of this kind would often appear in later-formed species without the aid of Natural Selection, or with its aid if the characters were of any advantage.” i.e. the 6th edition of 1872, in the new chapter entitled “Miscellaneous objections to the theory of Natural Selection”.
p. 344: “Before I had read your final remarks, I thought also that unfavourable conditions might cause through the law of growth, aided perhaps by reversion, degradation of character. No doubt many new laws remain to be discovered. Permit me to add that I have never been so foolish as to imagine that I have succeeded in doing more than to lay down some of the broad outlines of the origin of species.”
5. 1888: The Descent of Man and Selection in relation to sex. 2nd Edition.
p. 61: “… I now admit… that in the earlier editions of my ‘Origin of Species’ I perhaps attributed too much to the action of natural selection or the survival of the fittest. I have altered the fifth edition of the “Origin’ so as to confine my remarks to adaptive changes of structure; but I am convinced, from the light gained during even the last few years that very many structures which now appear to us useless, will hereafter be proved to be useful, and will therefore come within the range of natural selection.… I did not formerly consider sufficiently the existence of structures, which, as far as we can at present judge, are neither beneficial nor injurious and this I believe to be one of the greatest oversights as yet detected in my work. I may be permitted to say, as some excuse, that I had two distinct objects in view; firstly, to show that species had not been separately created, and secondly, that natural selection had been the chief agent of change, though largely aided by the inherited effects of habit, and slightly by the direct action of the surrounding conditions. I was not, however, able to annul the influence of my former belief, then almost universal, that each species had been purposely created; and this led to my tacit assumption that every detail of structure, excepting rudiments, was of some special, though unrecognised, service. Anyone with this assumption in his mind would naturally extend too far the action of natural selection, either during past or present times.”
This is a translation of the conclusion to Croizat's 1977 Spanish paper on
Keywords: Croizat, Darwin, evolution, laws of growth, natural selection.
The article presented below is a translation from the Spanish of the “Conclusiones” (pp. 84-88) of Bol. Acad. Cienc. Fis. Mat. Nat. Caracas 37 (no. 113):15-90. 1977.
An original, closely litteral translation was communicated privately by Croizat and on his suggestion has been turned into better English for publication.
The conclusions stand as a remarkably clear and concise summary of Croizat's analysis of the significance and value of Darwin's evolutionary theories. Despite the fact that all his big books contain chapters of “Conclusions” the charge is sometimes levelled that Croizat never presented his main ideas succinctly. Hopefully this short article will help to destroy this myth, and at the same time encourage the critical thought and discussion characteristic of healthy science.
During the course of preparing the translation for publication I enjoyed the assistance of Christine Gamet and Robin Craw.
Botany Department, University of Otago, P.O. Box 56, Dunedin.
Absolutely fundamental is the conclusion that history of the advance of ideas. He has right to this on account of having publicised the concept of evolution in the biological world. Darwin was born and wrote at the right moment to do this quite efficiently.
It is on the other hand a gross, very grave mistake to confuse Darwin as an historical figure with Darwin as an exalted figure of the thinking of biology. Darwin is a sagacious observer but in no way an acute, logical thinker.
It is a fact that Darwin recognised that there are active in evolution two distinct elements, that is to say: (1) Laws of Growth; (2) Natural Selection; the Laws of Growth being on simple sight independent from Natural Selection. If he had ever been an acute, logical thinker, in sum a genius, Darwin would have tried to structure a theory of evolution under which the Laws in question and Natural Selection would attain—the two together—a degree of harmony in proper relation to their individual importance.
Instead of doing what an authentic genius would undoubtedly have done, Darwin busied himself with theorising headlong in favour of Natural Selection. There can be no doubt in regard to this because Chapter VI of Croizat's original quotation is from a Spanish translation of Darwin 1872.The Origin of Species ends as follows: “The law of the Conditions of Existence is the higher law; as it includes, through the inheritance of former variations and adaptations, that of Unity of Type”.
It will be obvious that biologists—zoologists, botanists, etc., have rejected the Theory of Evolution of Darwin when informed that, as said by Simpson (1949, 23), tens of millions of species of plants and animals, quite distinct in appearance boil down to relatively few “Basic themes, general types of organisation”.
They have rejected it as notoriously incapable of explaining by Natural Selection (that is to say, through sums of haphazard variations supposedly advantageous to the organic being—better to say, the “species”—under its conditions of existence) the evolution of a fish into an amphibian; of an amphibian into a reptile; of a reptile into a mammal or a bird; of almost 9,000 “species” so markedly different among themselves as, for example, Ostrich, Penguin, Eagle, Sparrow, Goose or Hummingbird, all belonging to the same type of organisation of Birds.
These same zoologists, botanists, biologists, etc., have been willing to accept the theory of Darwin insofar as it is indeed probable that Natural Selection has favoured the differential formation of subspecies of birds, petty rodents, etc., belonging to the same proximal affinity isolated in different peaks or chains of mountains of the Andes, Caucasus, Himalayas, etc. In sum: The fundamental fault of Darwin's Theory is that it attempts to explain, regardless of cost, by means of Natural Selection that which this Selection explains at the best in a minor part. This fault is all the more serious in that said Theory seeks to impose as essential—whether one likes it or not—criteria of “advantage” of essentially popular type, lacking because of this actual scientific value.
However, we should not forget—even in the case of our being favourably disposed toward Natural Selection as a genuine factor of evolution—that it is possible to account for examples and cases of evolution in which Natural Selection is actually involved without for this making explicit mention of it. The affirmation that Natural Selection has eliminated during the Tertiary an enormous number of herbivorous mammals of Argentina stands unchallengeable, quite as much as the affirmation that an enormous number of herbivorous mammals of Argentina died out during the Tertiary, mainly because the gradual rising of the Andes changed, on account of desiccation and repeated depositions of alluvium, the lush slopes which once fed masses of herbivorous mammals into sterile stubble. In this case: Natural Selection equals desiccation and repeated depositions of alluvium. In sum: it is accordingly wholly feasible, indeed correct to specify in each case how “natural selection” happened to perform without appealing to it in the Darwinian manner as an agent of transcendental significance. It can thus be demonstrated that Natural Selection enjoys but a measure of relative importance, and it is absolutely not the element orienting the course of evolution as claimed by Darwin and his followers.
There rules today after over a century of essentially futile controversies a tremendous confusion as to what Darwinism is essentially worth, and there is heard from all sides an empty manner of talk which uses words actually void of meaning (for example: selective pressure, orthoselection)
This catastrophic state of confusion, has indeed no reason to exist inasmuch as it is by now very clear and beyond dispute that:
(1) The “Theory of the Origin of Species by means of Natural Selection” of historical figure a status to which he has no right as a thinker. To stand by what Darwin wrote as a thinker on account of his holding the place of a simple historical figure is a gross mistake.
(2) “Anti-Darwinists” and “Darwinists” fall today into three different camps, namely: (i) Those who are firmly opposed to “Darwinism” (e.g. the author of this article), refuse to grant to Natural Selection a place of importance in organic evolution, and are inclined to appreciate development in function of: (a) molecular biology; (b) biogeography (panbiogeography), throwing out virtually, the whole of the Darwinian theorising; (ii) Those who are fundamentally Darwinists in appearance (e.g. Simpson), but constantly contradict themselves by insisting on Natural Selection as the orienting element of evolution, but at the same time accepting the type of organisation, oriented evolution, etc. These biologists, naturalists, etc., mix up the Darwinism to which they cling with the anti-Darwinism explicit in the facts which they accept, and are because of this effectively anti-Darwinists; (iii) Those who as it appears, are complete Darwinists (e.g. Gould), and insist that Natural Selection orients the course of evolution on account of its determining the “type of organisation” which most perfectly corresponds with the surrounding environment and is formed most usefully.1
(3) In substance, a naturalist is or is not opposed to Darwin and his followers in the very measure that he credits, or not, a high degree of importance to Natural Selection. In this regard Darwin does not deserve being followed simply because he is a poor thinker.
1. What Gould thinks in the last resort is not easily grasped, which is to be anticipated whenever we are faced with the task of clarifying the opinions of a follower of Darwin. Because of this, he who may try to bring into light these opinions runs the risk of being charged with having misunderstood. It is at any rate certain that Gould did write (1976, 28): “The essence of Darwinism lies in its claim that natural selection creates the fit. Variation is ubiquitous and random in direction. It supplies the raw material only. Natural selection directs the course of evolutionary change. It preserves favourable variants and builds fitness gradually.” There is much more that could be added, but I am satisfied with what we have already learned. I will remark: (i) it is certainly true that the variation elaborates the stuff on which Natural Selection comes to work; (ii) it is on the other hand radically false that variation but casually proceeds (“is random in direction”). This cannot be because the variation is subjected to “oriented evolution” and “type of organisation” which Simpson accepts without doubt.
It is true (Gould, op. cit. 28) that: “Natural Selection has a place in all anti-Darwinian theories that I (Gould) know”. However, in the anti-Darwinian theories, blessed Natural Selection does certainly not assume the place it does in Darwin's own theorising, etc., etc. It is frankly very difficult to wallop the Darwinists because it is extremely difficult to find the place where to punch. Whatever the case in the end, one meets a mattress of notions mostly contradictory, and never clearer than those of Darwin himself. May they all stew in their own juices!!
The Theory of Geographic Distribution of Darwin is the progenitor of the “zoogeography” of Matthew, Simpson, Mayr, Darlington, Hershkovitz, Haffer, Reig, etc., and of the “biogeography” of Hennig, Muller, etc. All of this is pseudoscience essentially rooted in centers of origin, migrations, means of transportation that even Darwin himself proved unable to clarify, and are not worth being taken up seriously. See all my works. (Nelson 1973, provides a partial bibliography).
Finally, today quite as in years past (Croizat 1964:363, 374, 452, 723, etc.) I am firmly convinced that the basic rules of organic evolution through space and time can be summarized as follows:
(I) “Natural Selection” Comes to Work on What Orthogenesis Contributes. This means that Natural Selection is not the creative element of development; it prunes and lops out at best, and lacks the power to generate. Its field of action is restricted as a matter of fact to the subspecies and species. The idea that evolution marches on through the summing up of favourable variation ad infinitum is obviously and radically false. Equally false is the opinion that what is “useful”, “advantageous” for the individual and the “species” constitutes a fundamental criterion of evolution. No significance whatsoever attaches in science to the claim that what is now “useless” might have been “useful” in the past or “profitable” tomorrow. Mutation, and especially mutations oriented in series (macro-mutations), constitute the fundamental element of development, the agent that effectively creates the type of evolution. This means that the elements internal to the being (inheritance, capacity of undergoing change) much exceed in importance the external ones (natural selection, adaptation to the environment). As I see it, internal factors rule in 75-80% of development. A hummingbird is a hummingbird before its being—by adaptation—a hummingbird of the coast or of the high alpine open spaces (paramos).
Orthogenesis is for me a term that certainly does not contain metaphysical connotations. Orthogenesis is in its essence what Simpson takes for granted as evolution oriented within the limits of the type of organisation.
(II) The Current Geographic Distribution of an Organism Results From the Vicariant Formation of Taxonomic Groups Having Part in it, not From the Byproducts of Migratory “Jumps” Effected by These Same Groups When Passing From a Supposed “Center of Origin” to Another With the Help of “Means of Dispersal” Frequently Said to be “Mysterious”, etc.
It cannot be denied that the boundaries of the geographic distribution of an individual of a group or individuals may alter in relation to climatic changes, etc. What is certainly inadmissible is the disorderly “migration” by sheer chance that is typical of the “zoogeography” and “phytogeography” of Darwinian tradition.
Finally, the theories of Darwin, which never have been well structured, lack significance for the biology of our times. That Darwin ranks as a notable historical figure on account of his having been a standard-bearer of the doctrine of evolution certainly does not mean that his ideas on the manner of performing of evolution are correct. If “The Origin of Species” had been published in the Spanish language in Madrid in 1829 instead of in English in London 1859 hardly anyone would have heard of such a book.
Croizat's 1961 book
Principia Botanicais reviewed in relation to previous and subsequent work by other botanists. It is shown to be a major contribution to developing effective methods for analysing and solving problems concerning the geographical distribution, morphology and systematics of plants. Croizat's analysis and synthesis of the factors space (geographical distribution), time (phylogeny) and form (morphogeny/symmetry) in evolution, and how this relates to particular groups of plants is discussed in detail.
Keywords: biogeography, botany, carpel, Croizat, homology, leaf, morphogeny, morphology, phylogeny, symmetry.
The main theme permeating Croizat's Principia Botanica (1961) is expressed beautifully in the terza rima from Dante used by Croizat to head the work:
Fai come quei che la cosa per nome
Apprende ben, ma la sua quiditate
Veder non puo, se altri non la prome.
(Paradiso XX, 91-93)
(“You are acting like someone who knows something by name perfectly well, but will never understand its true nature if someone else does not resolve it.”)
In the Principia Botanica Croizat sets himself the task of developing basic concepts which will lead to a deeper knowledge of the quiditate, or true nature, of plant structure. One would receive the impression, judging from most introductory texts, that the problems Croizat deals with, for example “What is a leaf?” and “What is a carpel?”, have been answered adequately years ago. Surely a keen student can easily acquire knowledge of a particular plant organ by turning to the glossary often provided in modern texts and find a simple, easily learned definition? Comparative plant morphology defines the various plant organs essentially in terms of given categories. The plant shoot is considered as being fundamentally composed of two types of elements, leaf-like (phyllome) and stem-like (caulome), and the plant root comprises a third element. These elements are imagined to have been modified in many different ways to result in the variety of form which is the subject matter of comparative morphology. The flower, for example, is explained as being an aggregate of modified leaf-like appendages, some of which bear ovules.
The morphological research programme which effectively began in 1790 with the publication of Goethe's Versuch die Metamorphose der Pflanzen zu erklären (see Arber 1964 for an English translation and commentary) gained momentum rapidly. Over the last two centuries it has led to the accumulation of an immense body of factual knowledge. These facts naturally constitute problems—they must be explained. As outlined above, traditional ideology explains a particular organ as a modification of one of the three pre-existing categories. Morphological problems are presented by organs which do not fit easily into the conceptual framework offered by the accepted categories. In these cases botanists, who must be technically highly skilled, are often inclined to undertake research on the microscopic
A fundamental problem with the traditional body of theory is that the categories used in the definition “explaining” the organ are themselves understood poorly, if at all. One example is the definition of “carpel” as a “leaf-like organ bearing ovules”. Apart from such thoroughly un-leaf-like carpels as those of Arachis, the peanut, and Hakea with its interfascicular cambia, the definition is of course useless, unless we have a prior, adequate understanding of what we mean by “leaf”. The man in the street may feel that a leaf is simply a plant part which is flat and green, but for a botanist familiar with even a small part of the range of plant diversity this definition fails very soon. The fact is that we simply do not have sufficient understanding of what consititutes “leaf” to make the simple homology of “carpel” with “leaf-like organ bearing ovules” mean anything useful at all.
Our morphology must be based on a minimum of sound and fundamental concepts, and Croizat argues that this is precisely what is lacking from present day botany, since most authors have been content to simply homologise among themselves completely unanalysed organs.
For many botanists the main problem with the traditional research programme is a practical one—it has simply ceased to provide new ideas which can be used with effect to attack old problems. Thus in 1946 Dormer wrote:
“A striking feature of botany as the science exists at present is the lack of any coherent body of comparative morphological doctrine dealing with the angiosperms”.
Twenty years later Sattler (1966) echoed these sentiments:
“Relatively little progress has been made during the last 100 years in the study of the ‘comparative’ morphology of higher plants.”
This is surely cause for a reassessment of the bases of our knowledge and, even more importantly, our methodology.
Of course, the traditional research programme is by now such an integral part of botanical training and research that it would appear to be extremely difficult to change it. Meeuse (1966:29) has stated:
“Both Takhtajan…and Eames…
whilst adducing corroborative evidence in their argumentation, minimise or misrepresent contradictory findings and often dismiss dissident opinions and alternative theories with a summary self-assurance that verges on contempt. They write with so much self-assumed authority that the inexperienced student may be completely overawed and is likely to accept their apodictic statements as the “last word’ in a particular branch of botany. Adoption of scientific principles by accepting the teachings of an “authority’ was a medieval (“scholastic’) tradition—‘ Both botanists of the traditional school.
Galenus dixit’—it is certainly not promotive of educating a budding scientific mind towards independent thinking.”
And in a sympathetic review of Meeuse's book Cutter 1966 has stated, rather more diplomatically but to the same general end, that:
“Plant morphologists, in general, tend to be a somewhat conservative
group. One has only to read the reception accorded to the hypothesis put forward in 1908 by W. H. Lang, on alternation of generations to concede that, historically, novel viewpoints in this field have tended to encounter opposition”.
Despite this conservatism and invocation of authority, both hardly conducive to scientific progress, there is every indication that the botanical literature of the past decade reflects a growing awareness of problems raised in the Principia Botanica, and also of the value of many of the suggestions made in Croizat's work towards improving the situation.
It will be disconcerting to many botanists that Croizat's analysis of plant form begins with a thorough analysis of the dispersal of the carnivorous plants and their allies. Step by step Croizat methodically establishes that Droseraceae, Nepenthaceae, Sarraceniaceae, Lentibulariaceae and their relatives have, in fact, evolved stressing the same ancient, cardinal biogeographic nodes as angiosperm development itself. This conclusion is totally novel and thus, of course, unexpected, but it is based on a well documented argument which, while being lengthy and complex, is logically reasoned. Rather than agree or disagree with the conclusion on the spot the reader would be best advised to read Chapter 2 of Principia Botanica first, and then decide where he or she stands. The dispersal of the carnivorous plants (for example the striking vicariism displayed by Nepenthaceae with respect to the main massing of carnivorous forms in Australia, and also to the closely allied Dioncophyllaceae in West Africa) indicates that these taxa are not derived independently from other extant angiosperm families, as is commonly thought, but are instead the result of differentiation of a widespread ancestor. The actual tracks featured in their dispersal (for example Usambara (Tanzania)—Madagascar—Drakensbergs (South Africa); Duida-Roraima (Venezuela)—Futadjallong (Guinea)—Cameroon) point to an ancestor as old as angiospermy itself. As Croizat states, these ideas can be related closely to those of Huxley (1888) on the ancestry and evolution of Gentiana. Nevertheless, Croizat's analysis is considerably more extended, and provided early evidence for the geologically hybrid nature of North America (Princ: Fig 8, p. 79 and see p. 11 this issue) (geological heresy in 1961, but see Nur and Ben-Avraham, 1982), as well as providing strikingly novel interpretations of carnivorous plant evolution in space and time.
Maguire and Ashton (1977) have commented that Croizat's work is “studded with prescient insight” but in a review such as the present it is perhaps more important to emphasise Croizat's method rather than apparent “prescience”—his conclusions are due, after all, to effective analysis rather than lucky guesswork!
It is traditionally assumed that the carnivorous plants form an assemblage that is “artificial” in evolutionary terms, resulting from convergent offshoots of various extant taxa such as Saxifragaceae, Scrophulariaceae etc. This assumption is a consequence of essentialistic thinking in morphology whereby leaf, stem and root comprise the original, irreducible categories. Notorious among traditionally minded botanists are carnivorous plants such as Utricularia (Lentibulariaceae) in which it is often impossible to distinguish organs corresponding to any of leaf, stem
a priori notions of the fundamental nature of the categories leaf, stem and root, felt that the ideal angiosperm would naturally display these organs in their purest, most unsullied form. Thus pre-evolutionary doctrine regards these plants and their organs as degraded—to the extent that in them the pure morphological categories are no longer recognisable. That these plants must cause discomfort is evidenced by the infrequency with which they are discussed and illustrated. The transition from pre-evolutionary botanical thought to the acceptance of an evolutionary interpretation must be recognised as a great conceptual advance. But the necessary revisions of all aspects of botany were not carried out. In fact, as Sattler (1974a) has established, botanical research and teaching is plagued still by the pre-evolutionary essentialistic morphology. Nowhere is this more clearly evident than in the maintenance, albeit disguised, of the dogma of leaf, stem and root as fundamental and primal. This dogma is itself perhaps nowhere more firmly established than in the conventional interpretation of the “derivative” nature of the carnivorous plants.
This pseudoevolutionary interpretation proceeds as follows: Given that in angiosperms leaf, stem and root are “primitive’ (the old concept in its new guise), and given that many carnivorous plants and their allies show no distinction between these categories, then it follows that the carnivorous plants must be derived. But as, Croizat contends, any evolutionist must agree that the first premise of the argument is unwarranted. In fact, Croizat's analysis of the carnivorous plants indicates that many of them, and their allies, e.g. Podostemonaceae, represent an early level of angiosperm evolution at which the modern leaf, stem, root distinction has not yet been attained.
Over recent years evidence has continued to accumulate which points to the consanguinity of the carnivorous plant assemblage. For instance, Marburger (1979) examined the microscopic structure of the stalked and sessile glands of Triphyophyllum peltatum (Dioncophyllaceae). Unlike gross morphology, this is an aspect of anatomy least likely to show convergence if the groups are truly unrelated. Nevertheless Marburger found that the structure of the glands were “remarkably similar” to those of Drosophyllum lusitanicum of the Droseraceae. Likewise, Adams & Smith (1977) have illustrated the many morphological similarities, both gross and microscopic, among the five genera of pitcher plants.
Lentibulariaceae is closely linked with several other carnivorous groups through its very diverse members. The whorled Utricularia tabulata connects the family with the Hippuridaceae. Through the U. “avesicaria” group Lentibulariaceae is allied with the Podostemonaceae. The pitchers and traps of the U. “Dichotoma-monanthos” aggregate, as well as Genlisea and Cephalotaceae establish morphogenetic links with the Nepenthaceae.
At this level of evolution the transition from floral zygomorphy to actinomorphy is easily achieved—for instance through Cladopus, Dicraeia, Inversodicraea, Castelnavia, to Jenmaniella, to Dalzellia, Apinagia, Loncostephus and Tulasneantha all in Podostemonaceae. Thus the zygomorphic flower of Lentibulariaceae is not at all necessarily remote from the actinomorphic flowers of Droseraceae, Nepenthaceae and Cephalotaceae. The flower of Parnassia connects Droseraceae and Saxifragaceae. Through the Sarraceniaceae, Nepenthaceae and Dioncophyllaceae the carnivorous plants are connected rather directly with 20-30% of angiosperm families. For example, Airy Shaw (1951) and
Hippuris carpels is clearly competent to produce a normal halorrhagidaceous flower. Thus Hippuridaceae form a morphogenetic link between Podostemonaceae on the one hand, and Halorrhagidaceae, Gunneraceae, Lythraceae and Onagraceae on the other.
Lentibulariaceae and Droseraceae are bound by Byblidaceae (and Aldrovanda) which also serves to bring together Cheiranthera (Pittosporaceae), the actinomorphic Pittosporaceae and the more or less zygomorphic Ochnaceae.
The conclusion of Croizat's analysis thus point to the carnivorous plants and their allies as representing a level of evolution underlying all of modern angiospermy, and not at all as a derivative group.
It may be pointed out here that unless the botanist is prepared to take Croizat's conclusions on faith, which is hardly what the author intended, he must first gain a knowledge of the diversity of plant form rather wider than that taught in degree courses at most universities. An excellent way of achieving this basic familiarity is through living and studying in the vicinity of tropical rainforest, although this must be supplemented with time in the herbarium, garden and library. Illustrated floras of large tropical regions, epitomised by the Flora Malesiana, are invaluable. One or two volume synopses of angiosperm families are of limited use only, works by Baillon (1871-1888) and Engler & Prantl (1924-) give a much more satisfactory impression. Croizat's sound advice to the student is clear—look hard and long at the plants and the pictures, and ignore written description, to begin with, as much as possible.
After analysing the transection through angiospermy represented by Podostemonaceae—Theaceae—Lythraceae, Croizat continues his analysis of floral morphogeny with an examination of the level of floral evolution attained in the Amentiferae (Fagaceae, Betulaceae, Juglandaceae, Balanopsidaceae, etc.) Although Croizat's interpretation of the evolution of the modern flower is contained in his analysis of the carnivorous plants, the main argument is in Chapter 4 of the Principia. This chapter provides the factual basis for interpretation of Hamamelidaceae as representing morphogenetic transition between the level of floral organisation attained in the Amentiferae on one hand, and Davidiaceae, Garryaceae, Nyssaceae, and Cornaceae on the other. Thus a further transection of angiospermy is examined, and in the process Croizat's novel analysis of floral morphogeny emerges.
The nature of the flower is one of the most interesting and popular problems in botany. The range of floral diversity can be exemplified by considering a Magnolia or monimiaceous flower together with a single tiny flower of a Betula catkin, fig sycone or saururaceous inflorescence (see Fig 1 a and b).
For various historical reasons the former kind of flower came to be looked upon as “primitive”, and the latter kind as “secondary”, being derived, somehow, from the first. Guedes (1979:325) has succinctly described the process whereby:
“I.
W. Bailey became interested in wood, and generations of students had to learn the twists and turns of derivingNothofagusfromDrimys.”
These “twists and turns” are still taught in some universities but a growing number of botanists feel that rather than deriving one modern type of flower from the other we must rationalise the two in terms of evolution from a common ancestor. The actual structure of the ancestor may never be known, but hopefully we can begin by identifying some main morphogenetic tendencies in the evolution of modern forms. These tendencies must be established on a broad basis of factual comparison. Theorising on the basis of study of only a few forms will lead in many cases to unwarranted extrapolation, or simply uninformed guesses.
Floral evolution in Magnolia, Monimiaceae, Houttuynia and Betula can be easily rationalised within the concept of an ancestral strobile or cone. This is a matter of visual evidence (see Fig. 1 a, b) and is widely agreed upon. But what are the processes responsible for the reduction of this strobile to form the modern flower in all its diversity? Morphological definition establishes that technically the female sexualised scales in modern Magnolia must be termed carpels, whereas those in modern Betula and Houttuynia must be termed female flowers. But it must be noted that the development of stamens, or even incipient stamens as staminodes, on the carpellary wall is a simple matter in angiosperms (e.g. Yampolsky 1920)—it is simpler at least than deriving the Betula or Houttuynia type of flower from the Magnolia type of flower! This former process instantly relegates the Magnolia flower (Fig. 1a) to technical status of inflorescence (Fig. 1b) and the distinction between flower and inflorescence becomes blurred.
Thus, closely tied to any concept of the flower is the concept of carpel, and the limits between these two concepts.
In 1790 Goethe introduced the idea of the angiosperm carpel as being an organ of “leaf nature” bearing and enclosing ovules (the text-book “sporophyll”). This concept was also put forward by A. P. de Candolle in
“although no satisfactory definition of a leaf is thus possible I shall assume we all know what we shall be talking about”.
It seems clear that the identification of “carpel” with “metamorphosed leaf” is premature at best, and is probably tautological, representing no conceptual progress whatever. Not surprisingly, Satina (1959:146) states.
“It is obvious that the nature of the carpel is far from being settled and that additional information from different branches of botanical science is necessary for a radical evaluation of its true origin”.
In contrast with Goethe and de Candolle's homology of unanalysed leaf and unanalysed carpel, Croizat provides an analysis of the carpel which leads to fundamentally different conclusions. This analysis leads to the interpretation of gynoecial morphogeny as an interplay of two distinct elements—fertile placenta and sterile scale. The range of morphological possibilities rationalised by this single morphogeny is illustrated in Fig. 2. This analysis is becoming more widely accepted among floral morphologists. For example, Sattler (1974b) discusses the important consequences of accepting Croizat's:
“great achievement of demonstrating that ‘placenta’ and “gynoecial appendage’ (sterile scale) must be separated conceptually to cope with the whole gynoecial diversity including the carpellate condition in which gynoecial appendage and placenta(e) form a compound unit ((Fig. 2c))”.
Thus, the carpel itself does not form a basic gynoecial unit at all. (Croizat's scale + placenta may be compared with Melville's (1962) gonophyll equals leafy blade + epiphyllous fertile branch, but see Croizat 1964a:799 for further comment.) In the past the traditional Goethian interpretation has been forced upon many gynoecia, and
“as a consequence one has to assume arbitrary and imaginary lines of demarcation for which no evidence is available”. (Sattler 1974b:28).
Sattler describes this activity as “pseudoscience” (1974b:23). Likewise
“the carrying afield of ostensive definitions into regions where they do not apply, necessarily involves the crossing of the ‘high confidence’ boundary through the surrounding zone of decreasing confidence to the peripheral zone of meaninglessness”.
Much recent work has concentrated on gynoecia in which the ovules are borne not on the “foliar” gynoecial appendages as Goethe's theory predicts, but rather on the axial (cauline) portion of the gynoecium. This is one morphological possibility easily explained with reference to Croizat's analysis of gynoecial morphogeny (see Fig. 2a, b).
For instance, Maze, Dengler and Bohm (1971) and Maze, Bohm and Beil (1972) describe floral development in graminaceous plants in which ovules develop from the floret apical meristem. They interpret the ovules as cauline.
Macdonald and Sattler (1973:1972) conclude that
“the nucellus of
Myrica gale, as in a number of other taxa, must be considered terminal. The same conclusion applies to the ovule.”
They also observe (1973:1973) that
“Croizat's (1960 (Princ), 1962 (1964a) and Meeuse's (1966) frameworks offer a more satisfactory explanation of the morphological nature of the floral parts of
Myrica galethan does the classical concept”.
(They also note (1973:1966) that if these former concepts are used “M. gale would be interpreted to be primitive and perhaps preangiospermous (rather than considerably derived).” It is clear that these modern concepts of floral morphogeny have important consequences!)
Macdonald (1979:150) has described the wall surrounding the ovule in Myrica californica with the neutral term “circumlocular” and states: “It (the wall) is certainly not carpellary”. Stamens may be located on the wall.
Moeliono (1970:245) concludes an extensive study of the Centrospermae thus:
“I have rejected the concept of the carpel as a sporophyll. I have interpreted the ovary of the Centrospermae as being composed of a sterile abaxial part, formed by one or more congenitally fused phyllomes, and a fertile axial part (placenta,) the ovules of which are axis borne and thus of cauline origin”.
Van Heel (1973:273), describing the flowers and fruits of Scaphocalyx spathacea (Flacourtiaceae), stated that:
“although this pistil in its regularity would seem a most rational system, it cannot be understood under the classical carpel theory”.
Posluszny and Sattler (1976:1146) studied the floral development of Najas flexilis (Najadaceae) and showed that:
“the ovule is initiated in an exactly terminal (basal) position and not laterally on the gynoecial appendage (i.e. the gynoecial wall). Therefore it is not possible to apply the (Goethian) carpel concept to this situation”.
Pauze and Sattler (1979) discussing Ochna atropurpurea state:
“if it is agreed upon that axillary branches arise from the stem (caulome), then the axillary placentation of this species is also of cauline origin. It then follows, as a logical consequence that the gynoecium is acarpellate”.
Sattler and Perlin (1982) conclude work on floral development in Nyctaginaceae by observing that:
“the data of the present study do not support a carpellary interpretation of the gynoecium because the ovule is not borne on an appendage (megasporophyll)… Those who find the conclusion that the Nyctaginaceae
have no carpels too unpalatable might consider a re-definition of the carpel concept…If “carpel” is not defined as a foliar appendage (megasporophyll) which Bearsand encloses ovule(s), but instead as an appendage whichEnclosesovule(s), then the Nyctaginaceae are definitely carpellate”.
Once it is accepted that the carpels can most easily be interpreted merely as sterile scales which surround and may have fused with the placenta, the distinctions between ovary wall and integument, and thus between ovary and ovule, and between inflorescence and flower begin to break down. Van Heel (1967) agrees:
“In general I can follow Croizat in that there is a tendency for reproductive units to be sheathed by ever more telescoping coverings, leading from ‘ovules to ovary’ and from “flower to inflorescence’ or vice versa…The rating of the reproductive units (of
Scyphostegia) as ovules (as opposed to ovaries)…does not mean that we are closer to an understanding of their nature”.
Poszluszny and Sattler (1974) point out that the Potamogeton “flower” is “a structure somewhat intermediate between a flower and inflorescence …” Likewise, Charlton (1972) studying the inflorescence of the juncaginaceous Triglochin maritima suggests that “flower and inflorescence might well not be defined as different organ categories”. Sattler (1973) in his landmark “Organogenesis of Flowers” states.
“such structures which cannot be classified because they show characters of both a ‘flower’ and an “inflorescence’ are considered as flowers in this book. This does not mean that they are homologised with flowers; they are included simply for practical reasons. As there are intermediates between an “ovule’ and a “pistil’ intermediates occur between a “flower’ and an “inflorescence”’.
Botanists in New Zealand are aware of the essentially academic debate concerning the correct categorical pigeon-holing of the flower/inflorescence of Centrolepidaceae. Unfortunately the evolutionary view—that it is an “inflorescence” “caught” evolving into a “flower” (Princ. 516)—has not been considered in discussion.
Croizat's analysis of the angiosperm flower into whorls of scales representing a wide range of morphogenetic potential, plus the ovule-bearing placenta, leads naturally to the idea of the ancestral strobile or cone-like organ which has evolved by reduction, and redistribution of stamens and carpels into the modern flower. One defining feature of the flower is the germination of the pollen on a stigma formed from a portion of the carpellary scale. However, as indicated above, if the Goethian concept of carpel is rejected, then carpellary scales are in principle no different from the ovular integuments. In most angiosperms the stigma is provided by the “ovary wall”. However, in the urticaceous Myriocarpa and Leucosyke the inner seed coat forms, by means of a tubular projection, what “one might almost call ovular stigmas”. (McLean and Ivimey-Cook 1956:1440). In Myrica gale the stigma is provided by what can easily be interpreted as an outer seed coat. The gymnospermous Gnetum and Ephedra produce a thin micropylar tube (tubillus) from their inner seed coat, furnishing a normal, functional stigma. Thus the stigma can be produced by any one of the sets of scales surrounding the nucellus—inner seed coat, outer seed coat, ovary wall—and the boundary between gymnospermy and angiospermy begins to wear very thin indeed. It seems, in fact, to be artificial.
For Croizat, three alternative “morphogenetic gates” to the development of angiospermy from gymnospermy are represented by the flowers of Magnoliaceae and Nymphaeaceae; by the flowers of Monimiaceae and the
Betula (c.f. that of Houttuynia, fig. 1b) is formed through the development of the scales immediately surrounding the nucellus to form a stigma. Thus the strobile develops into an inflorescence, the catkin. In contrast, the Magnolia flower (Fig. 1a) is built up from the whole ancestral strobile, not just from the circumnucellar region, resulting in a pan-strobilar flower. Although the distinction between flower (Magnolia) and inflorescence (Houttuynia) may rest simply on the location of stamen development, the structure of both is easily accounted for by evolution from a preangiospermous strobile.
“Peloria” are structures produced, occasionally, at the apex of, for instance, Digitalis inflorescences, composed of the lengthwise condensation of part of the inflorescence. Several of the zygomorphic flowers fuse to form a strikingly new, virtually actinomorphic “flower”. In the Hamamelidaceae Croizat's concept of the role of peloria in floral morphogeny is easily seen. The typically zygomorphic amentiferous (circumnucellar) flowers of Distylium and Rhodoleia pass by a process of pelorisation into the (panstrobilar) flowers of the same genus (as abnormalities) or of Sinowilsonia, Sycopsis, etc.
It should be noted that, superficially at least, Croizat's-ideas on floral evolution are strikingly similar to many of those developed in the excellent, but almost totally overlooked work of A. D. J. Meeuse (e.g. 1975, 1982). Close parallels seem to exist between Croizat's ancestral strobile, panstrobilar flower and circumnucellar flower, and Meeuse's prefloral anthocorm, brachyblastic holoanthocormoid, and anthoid. These conceptual relationships will be discussed in a future article.
Chapter 5 of the Principia Botanica concludes the series of transections of the angiosperm families and develops the systematic implications of Croizat's analysis of floral morphogeny. The first conclusion is naturally that members of the woody Ranales are no closer to the ancestors of flowering plants than are any of a whole front of families on the threshold of angiospermy. As well as many of the woody Ranales and the “gate” families mentioned above, these families include Tetracentraceae, Trochodendraceae, Casuarinaceae, Leitneriaceae, Cercidiphyllaceae, Daphniphyllaceae, Eucommiaceae, Eupteleaceae, Salicaceae, Myricaceae and Tamaricaceae, all uninvolved directly with the woody Ranales.
These ideas find support in much recent work. For example, concluding a study of the wood anatomy of Daphniphyllaceae, Carlquist states: (1982:265)
“Some botanists are surprised to learn how specialised woods of such families as Annonaceae, Hernandiaceae, Calycanthaceae, Lactoridaceae, Myristicaceae, and Piperaceae are. Hamamelidales contain two families with primitively vesselless wood (Tetracentraceae and Trochodendraceae) and other families (Cercidiphyllaceae, Eupteleacae, and Hamamelidaceae itself) with strongly primitive woods…Thus the annonalean (magnolialean, lauralean) radiation was not the only radiation of primitive angiosperms, and our view of early angiosperms could well afford a more inclusive look.”
Leroy (1980) concludes that dicliny in Cercidiphyllum is primitive. Dilcher (1979:324) draws the following conclusions
“from the present fossil record of early angiosperm reproduction:
(1) Magnoliales should no longer be thought to epitomise the primeval angiosperm flower. The Ranalian Complex may represent one of the early lines of angiosperm evolution, but not singularly the most primitive. (2) The so-called “reduced” flowers of such orders as the Trochodendrales, Cercidiphyllales, Eupteleales, Hamamelidales and Piperales may be considered initially simple rather than reduced from a monoclinous (bisexual) ancestor. Independent lineages of some anemophilous flowers developed early and perhaps separately from entomophilous flowers from a common diclinous (unisexual) ancestral stock.
(3) Modern flowers are the product of a web of evolution…with repeating themes. The homologies of flower parts of various major taxa are complex, difficult and not presently well-understood”.
Another aspect of the origins of angiospermy is discussed by the eminent Russian palaeobotanist Krassilov (1973). He states:
“Another escape from Darwin's “abominable mystery’ (the origin of angiosperms,) is the theory of the upland origin of angiosperms. Their ancestors are then claimed to have been upland plants as well and not preserved in the fossil record…This is the best way to make the problem unsolvable
ab initio.”
Krassilov thus supports Croizat's severe criticism of the notion of an upland origin of angiospermy and states further that
“If the origin of angiosperms is still a mystery, the explanation should be found not in the gaps of the geological record but in the deficiencies of our evolutionary concepts.”
The idea that new fossil discoveries are essential for, and lead automatically to the resolution of evolutionary problems was criticised by Croizat and has recently come under attack both with respect to the origin of structures (e.g. Grierson and Bonamo 1979) and to the phylogenetic relationship of taxa (Patterson 1981).
Formerly seldom discussed, the idea of a polyphyletic origin of angiospermy has, since Croizat's work, been considered more and more seriously by many authors. Krassilov (1973, 1977) concludes that “angiospermous characters arose in several lineages of gymnosperms”, and in the latter paper cites Khokhrjakov (1975) to the effect that there is convincing evidence that monocotyledons were derived from gymnosperms. This interpretation of the palaeobotanic evidence is in accord with Philipson (1974:104) who adopts Croizat's concept of the “capacity (of angiosperms) to advance on a broad front”. Meyer (1970) discusses evidence from another source and proposes the “development of angiosperms over a wide area from groups already morphologically distinct”. In a 1977 review Merxmüller stated that “nobody seems to defend…a strictly monophyletic theory of angiosperm origin”. Anatomical studies of floral development by Maze, Bohm and Beil (1972) indicate that “flowers in general are polyphyletic”. Thus Johnson and Briggs' comment that “the monophyletic Magnolian theory is on shakier ground than many have assumed” (1975:90) seems more and more justified.
The word symmetry is often used in modern times to mean radial and even, as Weyl (1952) has noted, bilateral symmetry. The science of crystallography places no such restrictions on the idea of symmetry, and if development of general concepts of biological symmetry is desired we must likewise avoid any tendency to think that radial/bilateral symmetry is the only important mode. The study of biological symmetry is obviously of
As one example of a general, fundamental problem of biological symmetry we can examine the question “why do components of organic structure so often possess symmetry based on five”? It is often observed that among flowers symmetry of five is most frequent. It is less well known that sometime around 1510-1516 A.D. Leonardo da Vinci determined that in many plants the sixth leaf stands above the first (Richter 1939), this being perhaps the first reference to what later became well known as 2/5 phyllotaxy (the system consists of repetitions of five leaves in two turns of the axis). This is the most common of all patterns of leaf arrangement. In the animal kingdom symmetry based on five is manifest rather less obviously, but even so recurs with such frequency as to constitute a phonomenon of general interest. That radiolarians furnish many forms with pentagonal symmetry will some as no surprise to those familiar with these beautiful animals. Examples include the Pentasphaeridae, the Pentinastrum group of genera in the Euchitoniidae, and Circorrhegma (Circoporidae) (Campbell 1954). The foraminiferan Pentellina pseudosaxorum exhibits a pattern of growth identical to phyllotaxy in mode 2/5, sectors of growth being separated by a difference of five members (Van Iterson 1907; Croizat 1964a:440). The Priapulida, a group of burrowing marine worms, possesses dental armature arranged on its proboscis in pentagonal whorls (Nichols 1967). Echinoderms, of course, show a striking adherence to pentamerism. Since the time of the earliest known amphibians 360 million years ago, five has been the dominant number of digits in tetrapods, reductions from five (e.g. in horses and birds) have been frequent, but increases occurring hardly at all, and then constituting abnormality.
The “biological rule of five” is discussed only seldom (Nichols, 1967, has discussed it with reference to animals), but Croizat, in Chapters 7 and 8 of the Principia Botanica has subjected it to a thorough analysis.
D'Arcy Thompson (1917) in a very influential work, unfortunately failed to realise that the key difference between the main modes of phyllotaxis is simply one of superposition. For instance in his fig. 327 “leaf” 1 is clearly superposed by “leaves” 14, 9, 6, 4 in Fig. 327a, b, c, d respectively, leading to modes 5/13, 3/8, 2/5 and 1/3. In describing the obviously distinct appearances of the phyllotactic modes Thompson failed to mention this, noting instead that “the mathematical side of this very curious phenomenon I have not attempted to investigate”. This simple oversight led to over half a century of deep confusion, with many authors bent on analysing the mathematics of this evidently very complex subject!
As with the general problem of biological symmetry, the concept of superposition must be primarily biological rather than geometrical. Biological superposition cannot require, as does geometrical superposition, the presence of an exact perpendicular. The analysis of biological symmetry which utilises essentially geometrical premises is similar in many respects to the analysis of plant morphology which begins with the given categories leaf, stem and root or biogeography which begins with casual migrations.
Utilising the concept of superposition, the symbolism “2/5 phyllotaxy” refers to an important biological reality. Phyllotactic modes of 1/2 (two leaves per turn) and 1/3 (three leaves per turn) represent the morphological consequences of a meristem producing the minimum number of primordia (two and three) in the lowest modes of symmetry—biradial and triradial. The minimum number of systems which can interact is, of course, two. Beginning with the two systems which themselves represent minimal symmetry, Croizat's analysis shows that an immediate result of interaction between 1/2 and 1/3 symmetry is, in fact, 2/5 symmetry, or symmetry in fives. As with 2/5, the other common modes of phyllotaxis, 3/8, 5/13 etc., also produce between two and three leaves per turn—i.e. 1/2 and 1/3 mark the basic symmetries.
Croizat concludes that whenever a system of many primordia evolves by reduction of parts (e.g. by fusion) or by increase in number of parts, the system will tend to the minimal symmetries of 1/2 and 1/3, and their first “sum” 2/5. This tendency is responsible for the establishment, at the level of coelocanthid fishes, of the morphogenetic premise which led for example, to the five fingers of Homo and for the reduction of the ancestral strobile around five sectors of growth which led to modern pentamerous flowers.
The genetic spiral, described by the developmental sequence of leaf primordia, is often assumed to have special significance for phyllotaxis. But by a constant, gradual displacement of primordia, phyllotaxis may pass easily from, say, mode 1/2 to mode 2/5. This is possible simply because both modes have two spirals of growing points (cyclosectors), just as modes 1/3 and 3/8 both have three. Thus the genetic spiral, while being descriptively useful, is interpretatively useless, since all phyllotaxies are composed of more than one cyclosector.
The evolutionary history of echinoderms would furnish excellent material for a study of the inter-relationships of minimal symmetries. Biradial, pentaradial, and possibly archaic triradial forms exist. Current debate is concerned with whether or not this trimerous stage occurred in echinoderm evolution (Philip 1979, Stephenson 1979), but unfortunately none of the students involved have related the problem to general concepts of biological symmetry.
Modern studies of symmetry and ontogeny have rejected the traditional reliance on adaptationist “explanations” of aspects of organic form. For instance Goodwin (1982a, b) interprets developing organisms as:
“entities with an extensive range of morphological potential, describable in terms of probabilistic fields which collapse…into specific morphologies”. (1982b:52).
These concepts parallel those of Croizat on morphogeny vs. morphology very closely indeed, which is interesting as they have emerged from what are usually regarded as distinct areas of study—ontogeny and comparative morphology. For Goodwin the probabilistic field properties are a function of “general organisational principles”. (1982b:53). As a consequence of this fundamental change of emphasis Goodwin has subjected the neo-Darwinist approach to a critical and severe analysis, and concluded:
“Once it is recognised that there are principles of organisation and laws of form in biology, these time-independent properties of the living realm become once again central to the subject…the realisation that genes do not generate biological form leads to a rather different view of the evolutionary process in terms of the potential forms of the organisms and their appearance of the earth.” (1982a: 111-112).
Thus Goodwin, like Croizat, would place the emphasis on Darwin's “laws of growth”, in contrast with the neo-Darwinist tradition of virtually ignoring them.
Working with rather different subject matter from Goodwin, the Russian palaeobotanist Meyen (1973, 1978) has argued at length for a greater emphasis on the study of “general structural principles” (again corresponding to Darwin's “laws of growth”) independent of phylogenetic considerations.
Baas (1982), discussing the evolution of wood anatomy, criticises “rigid adaptationist interpretations”, advocating the important role of “functionless trends imposed by correlative restraints…”
The question “What is a leaf?” is certainly one of the great problems of botany. As mentioned above, the current state of despair is well exemplified by the comment:
“Although no satisfactory definition of a leaf is thus possible I shall assume that we all know what we shall be taking about.” (Gregory 1956).
It is clear that the definitional approach, using morphological, especially anatomical, criteria has failed to supply us with efficient concepts involving the true nature of the leaf. If we agree that the assumption “we all know what we shall be talking about” is hopeful but unfounded, we must also agree that it is necessary to do something.
It is Croizat's contention that descriptive anatomical criteria cannot supply an answer to the question “what is a leaf?”, and are, in fact, an inappropriate basis for evolutionary studies. In support is the comment by Schmid (1972:442) that it is Croizat who provides:
“the most pertinent and clear statement I have encountered regarding the problem of the validity of vascular conservatism”.
Croizat asserts that the most useful analysis of “leaf” would be in terms not of unanalysed morphological homologies, but rather of morphogenetic processes. With respect to Croizat's attitude towards interpretation of morphogeny vs. technical description of morphology, it is interesting to note Einstein's view that:
“It is really strange that human beings are normally deaf to the strongest arguments while they are always inclined to overestimate measuring accuracies.” (from a letter, quoted in Feyerabend 1978:58).
Croizat's analysis of leaf form and morphogeny (Princ. caps. 9, 10) includes consideration of many structures which were traditionally regarded (if at all) as unusual, insignificant, and, ultimately, accidental. Arber (1934:312) has summed up this unproductive attitude well:
“Another dictum of formal morphology is that the power of producing lateral shoots is confined to axes. When a leaf does, in fact, bear a shoot-bud, this shoot is described as ‘adventitious’, which means, literally, “accidental’. This is a typical example of the tyranny exercised by words over thought; just because they have themselves labelled these buds “accidental’, botanists feel justified in dismissing them as of no morphological significance.”
Just as “inexplicable”, thus “accidental”, patterns of dispersal (such as trans-tropical-Pacific) are analysed in his Panbiogeography, Croizat does not fail to consider the nature of “inexplicable” and “accidental” morphological facts in the Principia Botanica. The morphology of plants with structure problematical in the light of traditional interpretations has often led students, for example Jong and Burtt (1975) working on Gesneriaceae, to reject the “traditional morphological categories” as
The problem of the modern leaf was eliminated in the past, when “leaf” was proposed to be itself an irreducible category, an element, an essentially simple structure. The sociological and philosophical reasons for this proposition are complex—suffice it to say that Croizat begins with no such assumption. Indeed, by means of a thorough analysis of leaf form, Croizat demonstrates that, in fact, the modern angiosperm leaf is an essentially compound body (c.f. his analysis of Wallacean areas of endemism as compound entities). We are all aware of the complexity of leaf organogenesis, attained by a variety of meristems (Jeune 1981) and Croizat's conclusion may initially seem relatively innocuous. Nevertheless, it has important consequences.
Croizat approaches the morphogeny of the modern foliage leaf, stipules, cataphylls, buttress, buds and certain types of thorn (Cactaceae, Euphorbia, Fouquieria) as a general problem. As with the leaf/shoot question, rather than simply providing homologies between unanalysed organs it would seem more productive to inquire about limits between the organs, thus identifying processes of divergence. Croizat's analysis concludes in fundamental agreement with Tyler (1897) that the “lower foliar organs” (stipule, cataphyll etc.) are neither reduced leaves nor additions subsequent to the development of the modern leaf, but are the “primitive foliar organs”. The modern leaf represents a development of, and upon, this primitive leaf. The lateral portions of the primitive leaf, when separated, form the stipules, petiole wings etc. of the modern leaf. The sheathing petiole is a product of the development of the lateral and central basal parts of the primitive leaf—it is essentially distinct from the true petiole of the modern leaf. The leaf buttress represents the immediate continuation of the primitive leaf into the cortex.
These ideas are supported by studies of leaf organogenesis. For example, Cross (1938) has shown that in Viburnum cataphylls are not leaf homologues—cataphyll and leaf ontogeny diverge dramatically at the 80μ stage and leaf growth progresses by means of a distinctive ventral meristem which cataphylls lack. Bruck and Kaplan (1980) have shown that scale-leaves are not homologous with foliage leaves in Muehlenbeckia. In Morus, Cross (1937) found that the stipule development is unlike that of the foliage leaves, but like that of the cataphylls. Again the difference is fundamental, the foliage leaves being the result of the activity of a ventral meristem totally absent in the cataphylls and stipules. Thus the primitive scaliform leaf, represented by stipules and cataphylls, and the modern foliage leaf represent essentially distinct variants, at a very low level, of a single foliar type—the scale of Croizat. In the case of the foliage leaf, this scale or undeveloped phyllome has inherited a specialised “dab of meristem” which, once activated, leads to leaf organogenesis.
Macdonald (1981) stated recently that “The phylogeny of the stipule remains unresolved”, indicating also that little, if any, conceptual progress has been made since Sinnott and Bailey (1914) made similar comments sixty seven years earlier. Macdonald also noted that:
“to conclude that the stipules of
Comptonia(Myricaceae) are lobes or outgrowths of the leaf base, while true in an empirical sense, contributes little to our understanding of their phylogeny”.
However, recent work by Jeune (1981) concludes that, in the light of current knowledge of leaf ontogeny, Croizat's analysis is of special significance in adequately resolving the morphogenetic and phylogenetic nature of the stipule.
Macdonald concluded his perceptive paper by suggesting homology between stipule and prophyll (he unfortunately overlooked Croizat's analysis of “prophyll”, and his identification of it with “stipular sector” in Princ. 718).
Croizat's synthesis of the morphogeny of the modern foliage begins with verticils or whorls of primitive “leaves” (to be regarded more as phyllomes or primordia). As Howard (1974:160) has noted:
“The evolutionary progress from alternate and spirally arranged leaves to opposite or whorled leaves has become established as a dictum in most botanical publications…without any real evidence.”
Howard (1974:163) concludes that “the primitive leaf was probably borne in whorls or even vertically grouped clusters…”
These verticils, each of n “leaves” became suppressed, recombined and dirempted, or pulled apart, along the shoot into local sectors of (1 foliage leaf + 2 stipules (undeveloped leaves)). This process of reduction naturally takes place within the limits imposed by laws of symmetry, for example those outlined above.
What is the explanation for the development of the single leaf as the keystone of reduction and diremption of the ancestral verticil? The stipule/leaf distinction is not adequately defined by the presence of an axillary bud (e.g. Chaenomeles japonica stipules may have axillary buds), but histologically the distinction can be made on the basis of the ventral foliar meristem. The crucial question thus becomes “What is the phylogenetic and morphogenetic nature of this important meristem? What is its origin?” The only real answer given to this question is that of Croizat. The meristem is the product of ancient fusion of axes and primitive “leaves” leading to the modern leaf. The meristem itself represents the incorporation into the primitive “leaf” of the primordium of the ancient axis.
Fundamental to Croizat's analysis is the nature of the axillary buds observed in modern plants. Although some plants may have only one bud per axil, in principle there may be a series of axillary primordia lined up between the petiole and the axis. Today these are responsible for shoot-making of various kinds (floral and vegetative), including the fusion of epiphyllous inflorescences and leaves. In the history of the leaf, one element of these primordia has been competent in fusing an axis with the ancient “leaf” leading to the meristem which characterises the “modern” leaf. The relationship between the primitive scaliform “leaf” and the axis which it subtends and later fuses with is essentially hypocladial, in the sense of Kursner (1954). Hypocladial relationships between rameal and foliar organs are well known in many extant plants, for example, see Fig. 2. The axis which has become reduced and incorporated into the primitive scaliform leaf, leading to the development of the modern, hypocladial leaf could naturally be expected to have left some indications as to its nature— in other words the hypocladial transfusion may well not have been completed in every instance.
Dickinson (1978) in a timely and thorough review of the phenomenon of epiphylly has urged the study of the laws of growth which have determined the development of epiphyllous inflorescences. He has also noted the possibility of ephiphylly having been of “fundamental importance
Helwingia japonica Dickinson and Sattler (1975) state:
“The main conclusion is that such conditions (epiphylly) suggest that “laws of growth”…probably are as important, or more so, than laws of natural selection in determining plant form.”
The same authors (1974:8) in a study of the epiphyllous inflorescence of the saxifragaceous Phyllonoma integerrima state that
“our observations cannot be incorporated into the rigidly formulated classical theory of the shoot without distortion of the observations themselves, or of our understanding of them.” They also note that (1974:9) “The value of atypical situations like epiphylly is that they point out aspects of the real morphogenetic potential of plants in nature, corresponding to these “Laws of Growth”, that we often overlook.”
This potential may lie at no great depth, for example Stebbins (1965) describes the single “gene” controlling the production of epiphyllous inflorescences in plants of Hordeum trifurcatum (see Princ. 1533).
A question of crucial significance for an understanding of the leaf is posed by the nature of glands. Most recent work concentrates on their present day ecological significance and tends to ignore their morphogeny. But as Schnell (1970:433) has said, regarding extra-floral glands:
“Leur signification…parait a rechercher dans la morphologie et dans la phylogenie de la feuille plutôt que dans une utilité pour la plante…”
“An understanding of their significance would seem to require research into the morphology and phylogeny of the leaf, rather than into any usefulness for the plant.”
Since Schwendt's important 1907 paper, botanists have interpreted the morphology of plant glands as a result of the reduction of the hemming-in of pre-existent structures (e.g. see Schnell 1969:153-154 for discussion).
Glands, often secretory, are well known from the vegetative parts of many plants, as well as from the flowers. Particularly common are glands found at, or near, the petiole-lamina junction. Persistent meristems of various kinds have also been reported from this locality (e.g. Jong 1973 on Streptocarpus). Glandular teeth are well known on stipules (e.g. the rubiaceous Coprosma) and leaves (e.g. Chloranthaceae). The interpretation of floral and extra-floral glands as loci of hemmed-in tissue has been supported by Schnell (1969) with respect to domatia found in the axils of foliar venation (again Coprosma provides striking examples). He suggests that they indicate “une croissance avortée”. With respect to early theories on the origin of ant domatia by means of natural selection, Philipson (1964) cities Bailey (e.g. 1922, 1923) favourably, to the effect that:
“insects are not concerned with the origin of development of the structures”.
Thus there are many different structures present in the morphology of modern foliage which represent remnants of hemmed-in growth, and which must all be accounted for in any synthesis of leaf morphogeny. Howard (1974), in an important contribution, discusses aspects of nodal and petiolar form and concludes that these provide further support for Croizat's concept of the leaf and its essentially compound nature.
The question of the seed-plants' root has been answered even less satisfactorily by descriptive morphology than has been the question of the leaf. Descriptive criteria fail dramatically when faced, for example, by Lentibulariaceae, and, in fact, there are virtually no concepts efficient in producing even a minimum of understanding. In Chapter 11 of the Principia Botanica Croizat begins his discussion of the root with an analysis of the structures found at the junction of hypocotyl and root in the seedlings of various taxa. These structures (known in the literature as “wurzelhals”, “foot”, “peg”, “collet”, etc.) are much more widely distributed throughout angiosperms than was formerly realised, occurring in such taxa as Hippuris, Cucurbitaceae, Triglochin, etc. In Eucalyptus erythrocoris the normally horizontal collet forms a sheathing structure morphogenetically identical to the graminaceous coleorhiza. In the embryo of the seed plants, root and plumule, representing contrastingly polarised centres of development are joined by a transitional zone, the hypocotyl. Beyond the root initials lies the meristem (e.g. the rib meristem of Pseudotsuga—Allen 1946) from which arises the root cap. These three embryonal meristems are all bound within a jacket of ground tissue, Croizat's synthetic concept which comprises a sheath of considerable morphogenetic powers. The jacket is responsible for the development of various structures, for example tubers, napiform taproots, the collet, the haustorium of parasitic plants, the holdfasts and coralloid roots of the Podostemonaceae, the grass coleorhiza, and of course the rather inconspicuous cortical layer surrounding the hypocotyl in other “higher” plants.
The concept of “jacket” is an efficient tool for rationalising many aspects of root morphology from Pseudotsuga, to Triticum, to Utricularia. But a fundamental problem is offered by such plants as Podostemon ceratophyllum which have no distinct root but do possess a root cap. In fact Croizat recognises the problem of root cap as of fundamental significance. He suggests that it is advisable to maintain a general concept of rhizophore for what is currently termed “root”, “rhizome”, “runner”, “hypocotyl”, “pneumatophore” etc. in opposition to one of root cap. Thus the rhizophore is seen essentially as the bearer of the root cap, and structures such as the underground axis/rhizophore plus roots of the form genus Stigmaria, and the corm (rhizophore) plus roots of Isoetes, long considered problematical, are simply interpreted as relatively undeveloped morphologies in the morphogeny leading to angosperm roots. (c.f. Stewart 1947; Sporne 1975:69-70).
Croizat's analysis has not been developed by modern workers on the root, but it is clear that this is the least understood plant organ of all, and basic morphogenetic concepts are urgently needed. Too many recent studies of root form still provide “explanations” of that form in terms only of function and adaptation! Invariably aspects of root morphology apparently restricted to a small number of taxa are regarded as “advanced”,
This review has so far mentioned some of Croizat's work on the fundamentals of botanical philosophy, but it would be unwise to ignore altogether his contributions to other aspects of botany.
Croizat felt it was crucial to be able to place work and ideas in their historical context. In the Principia Botanica he seldom considers this as an end in itself, but the importance he placed on it and the interest it held for him can be seen in various other publications dealing largely with historical questions (1945) and biography (1949a, b).
Most of Croizat's early work deals largely with the taxonomy and nomenclature of Cactaceae and Euphorbiaceae, and is of only minor interest to the botanist who does not have a special interest in and knowledge of these families. In much of this work it is interesting to observe the enthusiasm with which Croizat dealt with the horticultural aspects of his favoured plants (e.g. 1941a). Practical rather than theoretical questions provided the impetus for all of Croizat's work which was not done in a vacuum but is of interest to all laymen and scholars who ask the question “Why is this plant the way it is, where it is?” It goes almost without saying that Croizat was a formidable enemy of ivory-tower scholasticism.
Because of the practical necessity of supplying a name for a plant, Croizat was naturally concerned with the correct application of the rules of botanical nomenclature, and also took an active interest in the development and improvement of the rules themselves (e.g. 1941b, 1953).
Croizat has published several large and important botanical works since the Principia. In Croizat (1964a, b) his ideas on angiosperm evolution in space, time and form are summarised and, to an extent, developed and refined. Croizat (1965, 1967, 1972a, 1973a) provide both an overview and a detailed analysis of Euphorbiaceae, Euphorbieae and Euphorbia and represent conclusions reached after several decades of cultivation and study of these plants. Croizat's work on these taxa is undoubtedly among the most important yet produced.
Croizat (1970) is a critical interpretation of Corner's fascinating but almost totally neglected Durian Theory of the origin of the modern tree. Croizat (1971, 1972b, 1973b) are very important contributions to the study of the leaf and of phyllotaxy, in which a considerable amount of new material is introduced.
Although the most striking aspect of the Principia Botanica is undoubtedly the fundamental nature and originality of the principles developed, the reviewer would be failing in his task if he did not attempt to place Croizat's botany in some sort of historical perspective. As with his biogeography, many of his ideas were hinted at, though scarcely developed by earlier students. Cusset (1982), in what must be regarded as a landmark of botanical historiography, has produced a review of the conceptual bases of plant morphology. In it the affinity of Croizat's concepts, particularly concerning foliation, with those of botanists such as Warming and Trécul is underscored. In the fields of floral morphogeny and high systematics
Many of the principles established in Croizat's work are becoming accepted, or at least discussed, by the botanical community, but too often the work is cited only by leading researchers examining fundamentals of botanical knowledge. Obviously even the reading of a large work such as the Principia is a major undertaking—much time is required to digest the arguments and check up on examples in field, herbarium and literature. But probably the main reason for the surprisingly small number of papers discussing Croizat's ideas is the fundamentally heterodox nature and the complexity of the analyses. As his ideas become more acceptable to the botanical community more credit will undoubtedly be given Croizat for the great significance of his contribution to the “Beginnings of Botany”.
This manuscript was submitted to Tuatara shortly before Croizat's death. It has been slightly edited by
In this posthumous paper, Croizat responds to criticisms of panbiogeography made by Ernst Mayr in two 1982 publications. The response emphaizes some of the key features in his approach to evolutionary biology and biogeography, including his views on disjunctive distributions, the Darwinian concept of dispersal from centres of origin, differential rates of evolution and the role of taxonomy in biogeographical analysis. The distinction between panbiogeography and vicariance biogeography is stressed.
Keywords: biogeography, Croizat, Darwin, evolution, Mayr, panbiogeography, vicariance.
Anyone assuming that the literature of biogeography is necessarily scientific is in for a surprise, when learning that this literature is all too often subservient to strictly human foibles of conceit, obstinacy, illogical reasoning, etc. It is imperative that young students be informed of this because, if not, they will find it impossible to judge correctly what the press and their surroundings offer for their attention.
When I began in the 1940s to take a positive interest in the field of the geographic distribution of animals and plants, I did not know that I was stepping into a field of research already dominated by a formidable duo: Drs. G.
The zoogeography heralded by Simpson, Mayr, Darlington, Dobzhansky, etc. needs not to be minutely picked apart for the benefit of the reader, when its very nature is made clear by the following opinion of Mayr:
“The distances between the various Antilles are so much shorter than the well substantiated jumps made by Pacific birds, I would not hesitate to accept transoceanic dispersal for the whole Antillean bird fauna without any major change of the present geological contours.” (Mayr; in Bond, 1948:208. c.f. Croizat, 1976:315; 1981:509)
The audacity of this fiat struck me on the spot as most remarkable, in no way compatible with the little I had already observed of the distribution of a number of plants in and outside the Antilles. If what Mayr was so unceremoniously handing be correct, zoogeography and phytogeography, respectively, must be antithetic sciences; a postulate that I rejected as if by instinct. If the whole of the biogeography of the Caribbean region could be reduced to a series of jumps (by no means “well substantiated” whether in the New or Old World, contrary to Mayr's extrarodinary claim) dispersal as a science of causes and effects had no longer reason to exist. Its most intricate problems could be disposed of with the affirmation that, e.g. Magnolia and Catharus have “jumped” from the Greater to the Lesser Antilles (or vice versa, who could say), using “means of dispersal” that, if absurd on the face of it could always be excused as “mysterious”.
To cut it short: to ask Mayr, Simpson, Darlington, etc. for light in point of dispersal meant to ask them for bread and fish—recalling the Biblical dictum of Matthew 7.9—but receiving in return stones and serpents. Left thus in the lurch by the luminaries of the day, who struck me repeatedly as but misguided theorists, I “invented” the “panbiogeography”. I can take little credit for such a discovery, because I was merely refurbishing the Method that four centuries before my time, had put Kepler in the condition of bringing down to earth the law of the skies. This method—it is by no means a Theory (notice the difference please!)—consists purely and simply in accumlating facts, finding a way to render them graphic by orbits of tracks, finally comparing them on a statistical basis in order to abstract the causes and rules of their being what they Factually happen to be. Naturally, even this method will not work if left in the hands of parties lacking disciplined imagination, and a certain amount of general culture qualifying its beneficiary to distinguish as between mere details and basic essentials and the will to take pains in the execution of a promising pain. Anyhow, whatever the case be in details, the Method stands, and triumph it shall against all manner of theories.
The panbiogeographic method—Panbiogeography for short—had me convinced in less than a month from the start that, as an instrument of investigation and positive knowledge it was infinitely superior to the zoogeographic theories trumpeted in the name of Darwinian “respectability” by Mayr, Simpson, Darlington, etc. The case of these gentlemen rested on the notion of a centre of origin of the “species” out of which the “species” would emerge migrating by particular means of dispersal. This notion did not survive for me even casual consideration, and I promptly rejected it feeling what Ball was privileged to experience some thirty years later than my beginnings, and to express in neat words as follows:
“For me, Croizat's contribution is one of liberation. Once we have escaped from the
necessityof seeking restricted centres of origin, and from thenecessityof plotting routes of dispersal from these centres, and once we have seen the possibilities unfolded by concepts of vicariance and differential form-making then a new world of ideas opens up for us.” (Ball, 1976:422)
Never has my lifework received a higher praise than in these few lines by Ball. Of course, they mean nothing particular for those who are not at all interested in new worlds of ideas, and cling like oysters to “Darwinian tradition” and its supposed respectability.
Sure of my grounds, and ready to continue my work, I did not scruple taking issue—in a spirit faithful to the form of convention—with certain weighty statements by Mayr such as:
“Dealing with the origin of the bird-fauna of Hawaii, an ornithologist (Mayr 1943:47) writes as follows, “There is not a single serious modern student (I use the term
seriousadvisedly) who believes in the former existence of land bridges between America and Hawii, or between Polynesia and Hawaii.” (Croizat, 1952:12)
Three years later, this author (Mayr 1946:12, 36) submits a diagram intended to elucidate the components of the bird-world of the Americas…, and explains that favourable conditions were lacking for tropical life to pass freely between Asia and America in the latitude of the Aleutians. This explanation is followed by a statement to the effect that,
“The close relationship between the Old and New World members of the Pantropical element, whose ranges are now widely discontinuous, proves that
such a faunal exchange must have taken place, and this places the zoogeographer in a real quandary. The customary solution for the problem is to ignore it… In view of the improbability of a North Atlantic land connection, various attempts have been made to find new routes for the transpacific migration. I Mayr shall refrain from a discussion of the various proposed transpacific land bridges. They are faunistically possible, but find no geological support. There is, however, some evidence for considerable recent tectonic activity in and south of the Aleutian island region, as well as for a pronounced lowering of the floor of the Pacific as a whole.” (Mayr, 1946)
So far for my comment on Mayr's zoogeography, to which I was careful to add:
“It is not our intention ((Croizat's)), in quoting these statements and bringing forth this map, to imply that the author in question Mayr is glaringly inconsistent. Consistency—as it has been shrewdly remarked—may indeed be a mere synonym of obstinacy”. (Croizat, 1952)
All in all, I felt that not even so exalted a figure as Dr Ernst Mayr could be offended by what I have just quoted. True, its substance was devastating and the method it heralded hard indeed to refute, but so is science, ever changing, as it might seem, for the better. If Mayr, Simpson etc., obviously stood mired in quandaries that their theories could not avoid, why should not Croizat be welcome in producing a notable breakthrough fit to help everybody around?
Thus anticipating a lively, readily constructive discussion for and against the nascent panibiogeography—surely at that time particularly, a less than perfect doctrine in every detail—I was greatly mistaken. All I heard after a time from friendly sources was that Croizat was being made the object of an active whispering campaign unfavourable to his character, manner of working, etc. None of the zoogeographic luminaries of the day came out to refute my viewpoints, to dismiss the panbiogeography as a brainstorm, but—now it can be told (see Abele, 1982)—Simpson let it be known that Croizat wrote from an insane asylum, and Mayr had him dismissed as a contributor formally and substantially of prose so remote from science that no serious student could entertain Croizat at all. The strategy against my work and person was indeed murderous: the very name Croizat was taboo, must not be mentioned, and some 10,000 pages of my work should be treated as non-existent. Had I been made of less resilient and durable material, I should take my scientific life as ended in 1952 and—why not?—induced to commit suicide.
Such having been the situation, for at least a quarter century may the reader imagine how great was my surprise when learning that Dr Ernst Mayr had printed in this very year 1982, two works, one a full fledged book, the other a review; rigorously keeping up the old anti-Croizat taboo in the book, but throwing it out of the window in the review. I could hardly believe my eyes, all the more so in that Simpson and Darlington to the best of my knowledge still unflinchingly refuse to recognise that a certain Croizat ever was born to the light of this rather poor world. It all was as if the Pope—in person of Dr Ernst Mayr—had sold out the Vatican and turned Lutheran.
The first of these two titles is, The Growth of Biological Thought, with subtitle, Diversity, Evolution and Inheritance, (1982b). Pages 448-455 essentially cover the part of the opus dealing with biogeography. The second title is the review by Mayr of, Vicariance Biogeography, by Nelson & Rosen 1981, (1982 a)
The Growth of Biological Thought Mayr clings to his old taboo forbidding even to mention the name Croizat. Not so at all in the Review in which Mayr relents to the extent of repeatedly naming Croizat and “Croizatians”!
From the standpoint of psychology these two titles, dated of the same year stand as a priceless document of the manner in which Mayr thinks. It is easy to see by comparing the two that, with or without the burden of the anti-Croizat taboo, Mayr labours under the heavy liability of showing the world that he was right even when wrong. His writings are accordingly eminently forensic (forensic is mild) and as such they must be understood.
In view of the unusual nature of the Mayriana I intend to bring before my reader, I will present the evidence in two major sections referring in one to Mayr under the anti-Croizat taboo, the other when free from it. In both sections, I will quote first Mayr's own texts and then immediately append my own comments. I thus propose to liquidate a situation which has stood in the way of a normally progressive advance of biogeographic knowledge during the last forty years. Doctor Ernst Mayr may be anything and everything to everybody, but in my deliberate opinion at least he has no title to pose as a genuine biogeographer quite as much in 1948, when teaching Bond how to “understand” the ways and manner of dispersal in Antillean range (see the introductory page of the present article), as today.
In the Growth of Biological Thought tidbits abound but only some I will bring before my reader. The main point of interest for us is to be found at p. 453, where we read:
“A somewhat eccentric biogeographic theory was proposed in the late 1950s, “vicariance biogeography”, which so far as I ((Mayr)) can understand it, stresses former continuities and downgrades the importance of longdistance dispersal… Quite logically, it found its chief support among ichthyologists, because primary freshwater fishes have a particularly low dispersal ability. Acutally, it does not seem that vicariance biogeography has introduced any new princples, since the occurrence of secondary discontinuities was already well known to Forbes, Darwin, Wallace, and other pioneers of biogeography (von Hosten, 1916). Darwin in particular was fully aware of the two causes for disjunction.”
Comment—This text, obviously referring to Croizat's Panbiogeography that came out of press “in the late 1950s” that is, 1958, holds a record for a maximum of inaccuracies, untruths and half-truths, tomfoolery, all in but eleven lines of print. The taboo forbidding Mayr to openly mention Panbiogeography is both noxious and ridiculous. And for the rest :(a) It is false that panbiogeography is a “somewhat eccentric theory” when it plainly is a positively constructive method of investigation of the records of geographic distribution of plants and animals, living and fossil, the world over. See Croizat 1952, 1958, 1960-1, 1962-4, 1968a, 1968b, 1976, etc; a bulk of organic literature in English, Spanish, French of close to 10,000 pages which Mayr nonchalantly wipes out for fuller misinformation of his credulous readers; (b) It is false to dump under the unfortunate designation “vicariance biogeography”, Croizat's panbiog (let us abridge this way the overlong word panbiogeography) 1952-1976, etc., and Nelson's highly theoretical mixture of Croizat's ideas and Hennig's sterile daydreaming (see: Nelson & Rosen, 1981, 1, 524; Nelson & Platnick 1981, ix, 543; Croizat, 1982); (c) What “vicariance biogeography” stresses is Hennig's “cladistics”. Panbiog rejects them and also
panbiog) because fresh-water fishes have a “particularly low dispersal ability” is false as a matter of fact (see e.g., Cyprinids in Croizat 1958; 1: 712 fn.; 2a:41, Fig. 124, p. 142 ff) and childish as an argument; (e) The statement to the effect that “vicariance biogeography” has introduced no new principles is ambiguous. Panbiog is something that “vicariance biogeography” is certainly not. Mayr has no clear understanding, if any at all, of the subject he believes to master; (f) it is possible that Forbes, Darwin, Wallace, etc. had visualised what Mayr calls “secondary discontinuities” (see next on this) without however using their “knowledge” to any efficient purpose. Darwin was “fully aware” of nothing much because being “aware”—as Mayr claims—of the “two causes for disjunction”, he wrongly argued nevertheless the whole of dispersal with or without discontinuities/disjunction/disconnections (see, Croizat 1962-4:631 ff).
If what Forbes, Wallace, Darwin, etc., managed to work out had been successful, the situation today would be different from the one Mayr paints (p. 452) stating: “The explanation of the origin of discontinuities has continued to be one of the most controversial subjects in biogeography”. Why so, Doctor Mayr?
Clear as I hope up to this point, let us pay close attention to what Mayr theorises about discontinuities (disconnections, disjunctions, etc.). This theorising is inspired to repeat Mayr's preoccupation with long overseas jumps, colonising flights and the like, which all, he imagines, gives the lie to “vicariance”, and therefore proves that Mayr has been right in the 1940s, while Croizat has been wrong at all times.
As a typical case of primary discontinuity Mayr imagines (p. 452) the following:
“A primary discontinuity originates when
colonistsreach anisolated areaand succeed in establishing apermanent populationthere. For instance, whenScandinavian insects and plants dispersed to Iceland in the post Pleistocene period, such colonisation, it is now quite certain, took placeacross a large watergap” (emphasis mine).
A secondary discontinuity (loc. cit.) originates owing to the
“fractionation of an originally continous range through a geoglogic, climatic or biotic event”. Adds Mayr without delay: “Unfortunately, the situation is not always…clear, leading to arguments as to whether or not
long-distance dispersalcould account for the discontinuity or, on the contrary, whether there is evidence for aformer physical continuity” (emphasis mine).
If, as Mayr himself admits, to attempt a distinction between primary and secondary discontinuities leads to arguments, therefore to normally sterilising confusion, I would say that it is considerate toward science and its devotees to abstain from insisting on premature definitions. A definition is in order when its subject is definitely known; but when the
explanation, not a definition is in order.
Mayr needs, however, definitions, whatever their merits as instruments of knowledge, which substantiate mentions of colonists reaching isolated areas across a large watergap by long distance dispersal. This breed of definition brings to the fore the paraphernalia of Mayr's zoogeography of 1940 vintage, which the development of the sciences of Earth and Life has killed for good during the last thirty years of slow grinding, (be it passingly remarked that panbiog had part in managing the funeral). It will still make an impression on the innocent reader however and induce him to accept as living the shadows of an empty past. I see no need of further expatiating on the primary and secondary discontinuities of Mayr when it is already clear that what is really in play is strictly propaganda and make-believe. Quite numerous and varied are the references to disconnection (discontinuities, etc.) in the indexes of my major work, and it is simply a false notion that discontinuities are, or still may be, one of the most controversial subjects of biogeography.
I see no further need to dig into Mayr's, The Growth of Biological Thoughts to have it proved with a great expenditure of printing space that Mayr is not reliable, labouring as he does under the weight of a silly anti-Croziat taboo and a constant obligation speaking from both corners of the mouth in order to refurbish a past surely dead. There is no rescuing today what for instance Mayr wrote in 1948 to Bond in adherence to a long, catastrophic line of opinionate, wrong zoogeography.
I cannot guest the reasons which induced Mayr to mention my name and work after some thirty years of a self-imposed taboo prohibiting it at all, in a matter of a few months of the year in course, 1982. All I know is that to my great amazement, Dr Ernst Mayr abruptly began to take notice of my person and work in the review, Vicariance Biogeography (of Nelson & Rosen, 1981), he contributed to the ornithological magazine The Auk 99: (618-620).
In this noteworthy piece of “Mayriana”, Croizat is abundantly castigated, reproved, etc., so much indeed that to furnish a fairly complete rebuttal I ought to write out a small volume. Since I have myself written about 10,000 pages in which Mayr stands firmly dismissed by knockout from the ring of scientific biogeography, I wil not now write this small volume. Those of our readers, Mayr's and mine, wishing to be quite clear on the issue will please consult, for instance, Croizat 1962-4. Their time shall not be lost in vain.
And now, in detail:
(a) op. cit., p.618—Mayr declares himself dissatisfied with Nelson & Rosen's 1981 book, and writes:
“In view of the considerable amount of uncertainty about the meaning of the two terms
dispersalismandvicariance, the reader would expect an introductory chapter with precise definitions and a clear formulation of the opposing viewpoints. Alas, there is no trace of such an exposition. Neither is Croizat's “panbiogeography” clearly defined, nor the termvicariance biogeography, apparently preferred by his latter-day disciples. The claim that “it derives its strength from the concept of relatedness, as expressed by…a cladogram” is evidently misleading because dispersalist explanations are just as much based on an analysis of relationship…Consistent with a current fashion, no opportunity is missed to denigrate Darwin and Darwinism… As the editors have failed to pinpoint the nature of the argument between thetwo schools and have badly misrepresented the views of their opponents, let me Mayr try to correct this deficiency”.
Comment—It is plainly useless that Mayr tries to “correct deficiencies” in a field that he does not know, nor will I bring here to record a long list of his errors, past and present, when I have pointedly spiked them over fifteen years ago in great detail. As to my “denigration” of Darwin, for example: Mayr has never read the motives of this “denigration” (Croizat 1962:4; 689 ff.), even less the “denigrations” of Gertrude Himmelfarb, whose strictures against Darwin, as a man and as a scientist, Gavin de Beer himself, Darwin's great admirer, could not dismiss as ill founded. After all: if Darwin had been indeed the genius who Mayr, Stephen Jay Gould, etc., delight in painting, it seems to me that his “great theory” would stand out of acute, constantly renewed controversies thus to match Kepler's and Newton's. Why should I waste my time and the reader's for the fun of pounding forever water in a mortar?
So, instead of wasting good print, just for pleasure to show the world bit by bit, piece by piece, I have driven eleswhere straight to the heart of the “Vicariance Biogeography” of Nelson & Rosen, 1981. May the reader please take good notice—which is usually not done—that the title in question has for its subtitle: Symposium of the Systematic Discussion Group of the American Museum of Natural History May 2-4 1979. Contrary then to what the near totality of biologists took for granted—I in the number—that Symposium did not have the purpose of ventilating the current status of biogeography in general: it was rigged up to promote the “biogeographic” opinions of a restricted circle of New York biologists having their headquarters in the American Museum of Natural History, of that grandiose city (Croizat, 1982).
Doctor Ernst Mayr knows of course nothing of this in his “review” of the failings of the New York Symposium which he pretends to censor, amend, etc. All he does is to insist on primary and secondary discontinuities, dispersal across the Bering Bridge, island hopping, colonisations across barriers, etc., in sum the flotsam and jetsam of the “zoogeography” that, as the humourless, stiff monoploy of Simpson, Mayr, Darlington, etc., managed to plague the world of science all the way from 1935 to the publication of Croizat's main works. The Mayrian claim (p.618) that:
“Prior to the discovery of plate tectonics and ocean floor spreading, biogeographers were forced to explain the old discontinuities as due to dispersal across the Bering Straits Bridge or to island hopping across the Indo—Australian archipelagos”
is of course spurious. As a biogeographer, I am “forced” to study only the biogeographic records of life, and to take logical account of what they reveal when objectively studied by averages the world over. What geological theories would say is of no account the moment these theories contradict the data from biogeography as such.
(b) (p. 619):
“If one finds trogons in the Old World and New World tropics, no “dispersalist” proposes that they dispersed across the wide Atlantic. Surely there was once a continuity, in this case perhaps the Eocene North Atlantic connections between Europe and Greenland. Actually, even the vicarianists cannot help but admit that distributions over an entire or several continents must have been the result of dispersal”.
Comment—Hidebound today, 1982, to his “zoogeography” of 1948, a taxonomist but not a biogeographer, Mayr stands under the hypnosis of
method of investigation—panbiog—, assured that evolution calls for constantly alternating spells of mobilism and immobilism; genuinely scientific biogeographers have precious little in common with the “vicarianists” fancied by Mayr for strictly polemical purposes.
(c) (p. 619): “The denial of dispersal forces the Croizatians into all sorts of eccentric geological theories. For instance, Croizat (p. 511) of ((Nelson & Rosen, 1981)) explains the Galapagos Islands as “a fragment of geological America, that was recast apparently in early Tertiary times, into a number of islands beset by volcanism”. The now-existing biota of the Galapagos is the product of evolution of the “ancient plant and animal life inherited as a whole from the American continent”.
This remarkable assertion, albeit the necessary consequence of “panbiogeographical” dogma, is so totally refuted by the geological and biological evidence that no further comment is necessary”(italics mine).
Comment—A further final comment is in order: what I have underscored of the text above quoted is a plain falsehood. What blinded Mayr to take the responsibility of having published under his name so blatant a falsehood is a mystery to me (e.g. see Brundin, 1981:123).
(d) (p. 619): “Croizat also misses the point that in the process of a multiplication of species, a new species always originates at a circumscribed location…One would think that Croizat, after he had got several pages of maligning Darwin out of his system, would proceed to provide evidence for the falsity of Darwin's belief that “each species has proceeded from a single birth-place”, but one searches in vain either for such a falsification or for a “superior” replacement theory”.
Comment—Doctor George Gaylord Simpson is an excellent, quite trustworthy author whenever free of an overwhelming enthusiasm for Darwin and Darwiniana. He ranks very high in my estimation when, for example, resuming the march of evolution and taxonomy jointly (Simpson 1961; 23) he writes as follows:
“The bewildering array of tens of millions of minor species of animals, ancient and recent, tends to obscure the broader pattern of life history. Endlessly diverse as these groups seem to be, they represent variations on a small number of basic themes, general types of organisation;… (p. 31) The various classes of chordates, for instance, will be shown to have appeared in the record precisely in the sequence that would have been predicted on the basis of their relationships and increasing divergence from or advance beyond a prototype”.
This is simple, clear and vouched for by a master of palaeontology and systematics when not, alas, biogeography. Once established—and there is no overwhelming difficulty in learning whence, for instance, the Type of Organisation of Aves materialised—the primary type of organisation ramifies out into secondary types giving origin under and within Aves in general to separate types of Ratitae, Sphenisciformes, Trochiliformes, Passeriformes, etc. The mechanism of differentiation consists basically of differential combinations of the characters particularly belonging to the type itself, by virtue of which we do not expect an Ostrich to come out of the egg of a Colibri. The atavistic “type characters” not only are combined and recombined, but also implemented by the play of macromutations
Whatever the details, the type of organization is the basic source of characters, and their eventual combinations to generate taxonomy.
Nobody will be surprised hearing or observing that group-characters can combine to reproduce at short distance virtually indentical phenotypes. Everybody—or nearly so—gets starry-eyed on the contrary when finding phenotypes that are virtually indistinguishable at great distance and in clear disconnection as, for example, Euphorbia on the highlands of the Caucasus and Armenia, and on the high-grounds of the loftiest peak of Taiwan. Everybody is non-plussed when learning that a lone species of the woodpecker Picumnus occurs in Southeastern Asia and part of the Greater Sunda, strikingly isolated from the bulk of the genus in Tropical America. Anyone familiar with Vavilov's parallel variations in plant life will accept without much ado the statement by Malcolm A. Smith (1935:7) that:
“((In lizards)) the same type of evolution is not confined to a particular genus or family, but may be happening independently, in different parts of the world, in species that are not directly related to one another…; (p. 357, quoting Essex) “I have some doubt as to whether Ceylon
Aconthias, ((a skink)), should be placed in the same genus as the South African ones, but, nevertheless, it is a closely related skink and belongs to the same stock, and is progressing along the same evolutionary path. I think it is more probable that the Ceylon species and the South African ones present the end of two divergent streams from an unknown centre.”
My feeling here is that no “unknown centre” is in play, only the well known standard track between Madagascar and India, which binds together many plants and animals.
Hearing this, many zoogeographers, cladists, disciples of Mayr, Nelson and Platnick, etc., will be raising an outcry that Malcom A. Smith and Croizat are a couple of innocents ignoring that skinks and like lizards are “tramps” always ready to use whatever occasional “means of dispersal” offer them a chance of performing spectacular feats of “extraordinary transoceanic colonisation”; therefore, the presumed consanguinity exhibited by skinks of South Africa and Ceylon-India is nothing but a “parallelism”, whatever parallelism might mean with these faithful custodians of the glory of Darwin.
This hardly credible, coarse, unscientific way of handling dispersal, whether with skink or “ballooning spiders”, etc., on the part of Mayr and his crew can, fortunately, be exposed referring to texts so precise, so easy of interpretation as not to leave doubt. To begin with, Mayr wrote as we already heard (see (d), above) a stern indictment of Croziat, saying:
“One would think that Croizat, after he had got several pages of maligning Darwin, would proceed to provide evidence for the falsity of Darwin's belief that “each species has proceeded from a single birth-place” but one searches in vain either for such a falsification or for a “superior” replacement theory”.
In presence of affirmation of the kind, I openly wonder whether Dr. Ernst Mayr is indeed compos sui; whether in sum Dr. G. Mayr instead of Croizat when visualizing somebody at the gate of an insane asylum. Darwin's belief that each species has proceeded from a single birth-place is stated in “On the Origin of Species”, Chapter xii, “Single Centres of supposed Creation” and reads:
“We are thus brought to the question which has been largely discussed by naturalists, namely, whether species have been created at one or more points
of the earth's surface. Undoutedly there are many cases of extreme difficulty in understanding how the same species could possibly have migrated from some one point to the several distant and isolated points where now found. Nevertheless the simplicity of the view that each species was first produced within a single region captivates the mind. He who rejects it, rejects thevera causaof ordinary generation with subsequent migration, and calls in the agency of a miracle…if the same species can be produced at two separate points, why do we not find a single mammal common to Europe and Australia or South America?…The answer, as I believe, is, that mammals have not been able to migrate, whereas some plants, from their varied means of dispersal, have migrated across the wide and broken interspaces. The great and striking influence of barriers of all kinds, is intelligible only on the view that the great majority of species have been produced on one side, and have not been able to migrate to the opposite side” (emphasis Croizat's).
This is plain nonsense, which disqualified Darwin with finality not only as a “genius” but as a decent thinker. Darwin was incapable of rationalizing the nexus between form-making (the “origin of species”) and dispersal (“migration”), and appeals to other people's ignorance to join his own, assuring everyone in the game that by compounding the truth it is being born! This is fantastic, and Mayr can be legitimately charged with lack of scientific integrity for having withheld from his readers the quotation I show to my readers as a strict matter of duty. Is there indeed any need to “falsify” Darwin's falsehoods? Who “maligns” Darwin more than Darwin himself? Why goes Dr. Ernest Mayr to war against Croizat firing only blanks? I do not do that: I shoot to kill, and sometimes I do.
A very live cartridge in my defence—if need for it be—is ready-made in the following text by Malcolm A. Smith:
“When I was revising the genus
Lygosoma, sensu Boulanger, I was surprised to find that a West African skink,Riopa guineense, was indistinguishable from one I had descrbed from Siam,R. herberti. There could be no question here of any geographical connection between the species: it was simply that the same set of characters had turned up twice. I think that this is what may have happened toLygosoma maculatumandL. dussumieri, and also toDasia olivaceaandD. subcaerulea“.
Zoogeographers, Mayrists, cladists, vicariant-biogeographers (a la Nelson) etc., will appeal to the most fantastic tales, to so argue against M. A. Smith that it is absolutely impossible that he is in the right. Stuffed up to the gills with stale Darwinian formulae, entirely wanting an idea of recombination of characters, of type of organisation, of panbiog in short, these heroes of a defunct cause still make a lot of noise, alas.
If we coldly reason on a strict basis of fact—the panbiogeographic way—we learn (M. A. Smith 1935:312) that the genus Riopa has over 30 species distributed from Africa over Southern Asia to Polynesia and Australia, a perfectly normal range for plants and animals (see Croizat 1958, 1960-1, 1962-4, 1968 a.b. etc). All over this immense sweep of land and sea, characters befitting the types of organisation pre-Riopa, proto-Riopa, sub-Riopa, s. 1., Riopa s.s. in turn held sway more or less broadly over the ages, depending upon the vicissitudes of geology, climate, ecology etc.; always, however, broadly enough to assure us that Riopa occurs today both in West Africa and Australia, for example, not by “ballooning” via the stratosphere or on account of a truly “extraordinary capacity for tanscontinental dispersal” in Mayrian style; just by the interplay of natural causes over space by time having eventually returned here and there like and unlike taxonomic form-making.
Now then: is it contrary to reason to accept as normal that a particular
Riopa species that are phenotypically (and taxonomically), obviously inseparable, therefore stand as a “single species” guineense-herbertin spite of distance? The “species” that is phenotypically one, will it also be genetically one? If sexual compatibility is the earmark of the “true species”, can we be sure beforehand that R. guineense male will accept as his sexual partner in procreation R. herberti female? In other words, what are the genunine relationships as between the phenotypic and the genotypic species, if any indeed. How is the conscientious naturalist to work out problems of this seemingly involved kind?
Before proceeding, let us record here a captial observation: a process is always more important than any of its byproducts. Riopa guineense and R. herbertiare separated by a distance of many thousands of miles as the crow flies. Lygosoma maculatum (Eastern Himalayas, Northcentral India, Assam, Burma, Southwestern China (Yunnan), Indochinese Peninsula southward to Tenasserim (Kra), Cambodia, Annam, Malaya, Andaman Islands), and its close ally, L. dussumieri (Southwestern India: Travancore mostly) stand at a glance at a much shorter distance from one another than do Riopa guineense and R. herberti. So too, Dasia olivacea (Tenasserim, Indochina south of 15° lat., Malaya, Andaman and Nicobar islands, Pulo Condor, Sumatra, Mentaweis, Natoenas, Java, Borneo) and D. sub-caerulea (Southern India: Travancore).
Assured for once that all these skinks answer the same biogeography, as to manner of taxonomic form-making and translation in space (“migration”)—indeed, it could not be otherwise as they all “move” within a close range of affinity—a competent biogeographer will not so much pay attention to the byproducts in detail as reckon on the process common to all the byproducts (genera and species: Riopa and Dasia, guineense/herberti, maculatum, dussumieri etc). This competent biogeographer will grasp the whole as nature herself does, not bit by bit as a shortsighted pedant will; as somebody in sum, who pays good coin to listen to a first rate concert as a whole, trombone with violincello, but can only argue that it is very droll that the trombone does not yield the same sound as the violincello. Shakespeare had it right: What fools these mortals be!
It is glaringly evident that she or he who does not understand the process will be in difficulty when trying to sort out its byproducts. It is a fact of the record that the zoologist and botanist lacking proper understanding of biogeography (correctly speaking, panbiog) will be unable to comprehend the reason why, for instance, phenotypes that cannot be set apart (see Croizat 1976; 1:338 ff.), prove to be sexually incompatible, which means that the very same “one species” phenotype proves to be genetically “two species”, If, of course, the test of sexual incompatibility is assumed as the final criterion of “speciation”. What is true of Troglodytes in the New World is no less true of Parus in Central and Eastern Asia (Croizat 1962-4:50g ff.), and, if with different details, of Gossypium (Croizat 1962-4:99).
In their unfortunate opus magnum, Systematics and Biogeography, (1981) Nelson and Platnick say (p. 6):
“The order in which the elements of space, time and form (and the respective disciplines primarily associated with them) are treated in this book is the reverse of the order…used in the title of Croizat's 1962-4 work. There are two reasons for this reversal. The first is that systematics, in providing classifications that summarise existing knowledge about the attributes of organisms, is a necessary practical prerequisite to the other fields. If our
systematics is inadequate, it will scarcely be possible to do adequate work in biogeography, paleontology or embryology. The second reason for this reversal, and one of the themes of this book, is that hypotheses about the history of organisms in time are tested by statements about their attributes, and that hypotheses about the history of organisms in space are tested by statements about their history in time…; (p. 7). Considerations of scientific methodology…typically involve questions that are philosophical rather than scientific. From this we can conclude that one's general philosophy of science may greatly influence methodological discussions and decisions, and that it is therefore incumbent on scientists engaging in such discussions or making such decisions to present, as explicitly as possible, the philosophical point of view from which they argue…; (p. 13). The ranks, or categories, of genus and species have a particular significance, for they are the basis of binomial nomenclature…; (p. 34). Science is a way of viewing things as problematical…and the evidence for classification is problematical and deserves to be viewed as such…; (p. 42). Of the three elements of comparative biology, space has undoubtedly proven to be the most elusive… Exactly why this should be the case is not easy to say. One factor might be that at least a tentative classification must be available before biogeographic investigation can begin: one must first know that there is a certain taxon before one can investigate either its distribution or the causes of that distribution. To some extent, then, biogeography must lag behind systematics.”
This striking exhibit of pedantry and misplaced “philosophical” pomp and circumstance impels its oversanguine authors to give pp. 64-328 to “Form”: pp. 331-353 to “Time”; pp. 357-543 to “Space”, ending with the abject confession that the opus on the whole has yielded nothing concrete, added nothing to present knowledge, which means in my understanding that Nelson and Platnick have merely worked to increase all around confusion, taking their cue from misleading starting points. This striking confession after having spent over 500 pages to no concrete purpose absolves me from the task of checking in detail these same pages thus to expose in great detail lapses of the kind proving indeed ignorance of fundamentals. Nelson and his coauthor Platnick are not authentic biogeographers, which I will show true and correct through proper references if challenged. Time is overdue to call the score in plain words. If there is anything with which to start in the objective investigation of evolution this will be found not in the ever-shifting labels of taxonomic study, but in precise biogeographic work (Croizat 1960-lb:1451 ff.; 1962-4: 4 ff. without specifying beforehand what I was dealing with, plant or animal). I have also insisted (Croizat 1962-4; 519-520) that, in cloudy cases of taxonomy, the subspecies supplies data more important and reliable than the species, on account of the subspecies being more precisely localised than the species. The brainstorm afflicting Nelson and Platnick, and their colleagues at the American Museum of Natural History of New York (see the opening pages of Virginia Ferris's review 1980 of the 1979 symposium) to the effect that systematics and taxonomy must come first before biogeography, and that one ought to be a vociferous “philosopher” before becoming a commonsense naturalist; could be dismissed as an infantile affliction, if it did not prove to be catastrophic as an agent of pointless chatter and confusionism. Yes, indeed, Nelson & Platnick, etc., are one with Mayr, whatever be the appearances. They see themselves as brilliant horsemen fighting the good war of “science”, but what kind of horses are they riding? To look them in the mouth is appalling.
Returning now to Mayr's review of Vicariance Biogeography (The Auk 99, 1981):
(e) (p. 619): “I believe all vicarianists are cladists…curiously, the Croizatians never attempt to falsify their own hypotheses.”
Comment—“Who are the “vicarianists”, and how should they be distinguished from the Croizatians? I, method that returns no falsehood? These boys are lost in a sea of make-believe, “cladism”, “Popperism”, etc., of their own making to the extreme that common sense, precision of language, clarity of thought mean nothing any longer to them.
(f) (p. 619): “classical biogeographers have again and again strictly applied the canons of the hypothetico-deductive method…In the 1940s there were two hypotheses concerning the colonisation by birds of the islands between the Sunda and Sahul shelves… The two hypotheses permitted numerous predictions based on the distances of the islands and depth of the water between them. In a thorough analysis, I was able to show (Mayr 1944) that the predictions of the land-bridge hypothesis could be falsified in every case while those of the across-water-dispersal hypothesis were thoroughly confirmed.”
Comment—Mayr's (1944) “thorough anaylsis” of dispersal in Australasia led him to settle the problems of Antillean dispersal in 1948 in the expeditious manner we have seen (p. 00 above). He who may believe the Mayrian “thorough anaylsis” of exchanges having taken place in bird life in the Sunda-Sahul region, has no understanding of the geology, indeed extremely changing, island by island, of the region in question. In autodescribing himself (with Simpson, Darlington, etc.) as a “classical biogeographer” Mayr exaggerates even in his capacity as a propagandist.
(g) (p. 619): “Perhaps the greatest weakness of vicariant biogeography is its endeavour to explain the distribution of very different groups, by a single ancestral process (“track”) and, furthermore, to place the time of origin of the distribution patterns as early as possible, mainly Triassic-Jurassic, occasionally up to the mid-Cretaceous period. In that manner discontinuities can be atributed to geological events, permitting a neglect of dispersal. As more and more evidence shows, however, most of the higher taxa of terrestrial organisms, up to the rank of orders, originated only in the later Cretaceous and in the Tertiary, and hence cannot have been inhabitants of plates that had drifted apart in an earlier geological period”.
Comment— The author of this text has no title I can see to speak as a scientific biogeographer. May the reader decide whether he does violence to the record because of gross neglect, occult malice or the like all over. See on track, Croizat, 1962-4: 7, 1960-1; 1b: 1615 fn.; etc.
(h) (p. 620): “There are two major factors that determine the distribution pattern of a group—its dispersal abilities and the geological period when most of the dispersal took place. This is why earthworms and primary freshwater fishes have totally different distribution patterns from birds or butterflies”.
Comment—This is false by the record (see all my works). Its author has no interest in the truth, only in defending at all costs his past dereliction as a “zoogeographer” of sorts.
(i) (p. 620): “Croizat's thinking is well illustrated by his interpretation of the origin of the bird faunas of Pantepui (Venezuelan highlands). They represent for him a pre-Cretaceous continuity, with the gaps between the various mesas and the Andes secondarily produced by erosion. Therefore the age of the allopatric subspecies and even the nonvariable species is postulated
to be greater than the length of the Tertiary. How can one take a biogeographer seriously who ignores the established ideas on the rates of evolution to such an extent?”
Comment—How can one take a “zoogeographer” seriously who distorts the clearest kind of factual evidence in order to build a factually calumnious case against a well informed, honest (pan) biogeographer? I never thought or said what Mayr charges me with. To explain: let us visualize, for instance, a fauna markedly “autochthonous” in which occurs at this hour side by side, a “modern” species of scorpion and a “modern” species of Thraupidae (passeriform birds). The record justifies the following questions: (i) Inasmuch as the two species A (scorpion) and B (thraupid bird) are today contemporaneous within the same fauna, does it follow that species A and B, respectively, are of the same age?; (b) Have the species A and B, respectively, entered simultaneously or not the fauna in which they occur today?
To answer these, and like questions is very easy if we reason the evidence logically, methodologically; impossible if we start with theories. Scorpions are a very ancient group, anterior to the Permian, while thraupid birds are a relatively recent group fully materialized only in the latest Cretaceous (it could not be later because it “colonises” with a multitude of vicariant forms the peaks and sides of cordilleras that rose mostly in Tertiary times). An already well defined, near-modern species of scorpion might accordingly have entered the fauna of which it is part today in the Jurassic, taking advantage of spells of mobilism and immobilism, in the geography, topography, ecology ruling at the time. In, let us say, Late Cretaceous, the primitive species, let us suppose, became extinct, leaving in its place a descendant species, the one surviving today.
The case is entirely different with Thraupidae. In the Jurassic, Thraupidae were non-existent which is far from meaning that they were absolutely non-existent for their remotest ancestors, some form perhaps of diminutive plumed dinosaur—for, had these potential ancestors never existed, their actual descendants never could materialise sooner or later that it be. Naturally, these remote “thraupid ancestors” went through Jurassic, Cretaceous, Tertiary repeated extinctions, new formations, etc., at a rhythm of evoltive change many times quicker than scorpions. In sum, once the types of organisation were established, scorpions—so far as we can know—moved on slowly, Thraupidae fast.
Being well informed of the march of events the world over, I could not think, of course, that the bird faunas of Pantepui (the southeastern Venezuelan highlands) represented “a pre-Cretaceous continuity” of Species with the bird faunas of the Andes, cordilleras, mesas of Venezula, Brazil, etc. The continuity postulated obviously was of Ancestors, out of which were locally to arise, in due course of time and events, the taxon geographically “pantepuian”, andean, etc. There can be no doubt whatever of where I always stood and still stand (Croizat 1976 Vol 2:563 ff.; Croizat 1952; 32 ff), and where Mayr got his lore from. He had it from F. M. Chapman (1931) (see Croizat 1952; 33), and during fifty solid years of “zoogeography”, “new systematics”, etc., it never occurred to him to verify his grounds and to progress accordingly so little as an inch. With eyes glued on the “species” as the supreme object of nature, Mayr refused to take me “seriously” because I ignored the “established ideas of the rates of evolution”, imagined by him! How unfortunate has been youth which for close to two generations has had to listen to such a
ex cathedra in Harvard University. What he has managed to achieve is written very large in the total disarray of general studies of evolution and biogeography in North America.
(1) (p. 620, end); “Reading the volume, ((Nelson & Rosen, 1981, Vicariance Biogeography)) however, made me hope that someday someone will undertake a truly rigorous analysis of the vicariant claims in order to demonstrate conclusively how flimsy they are.”
Comment—Please, Dr Mayr, do not undertake the job, for in my considered opinion, Dr Ernst Mayr lacks status to speak as a biogeographer. The record proclaims it with finality, and much else could yet be added to round the scores of this article. The truth must be told. By the way, whose are the “vicariant claims” your condemn? Nelson's or Croizat's?
Even the most obdurate optimist will not deny that biogeography is a field of fundamental biology plagued by an excess of conflicting crosscurrents. Most strong among these currents is the one Darwin did sire as the “Theory of Geographic Distribution”, in “On the Origin of Species” (Chapter xii: Geographical Distribution, Single Centres of Supposed Creation), and which is quoted on p. 57.
In relatively few lines, that text brings to the fore all the classical concepts of Darwin's Geographic Distribution. That is to say, the Zoogeography/Phytogeography of Simpson, Mayr, Darlington, Gould, hosts of zoologists and botanists, all of whom have tenaciously stood by Darwin, swearing by Unitarian origin of species, centres of origin, means of distribution, migrations, barriers, etc., to this very day. Vaguely aware that the discoveries made in the sciences of the earth in the last twenty years have ruined Darwin's theory of “geographic distribution” (today identified by a growing number of biologists as dispersalism), some brilliant young blades are hard at work scheming out new, ever more involved theories to show that Darwin, say what one may, could not be wrong. Some older blades (e.g. Ernst Mayr) indeed go so far as to deny that Darwin could have been substantially wrong in anything important.
Years ago (Croizat 1962-4; 631 ff.;etc.), I raised the question whether Darwin's text cited above could be accepted as a final expression of the Darwinian theory of dispersal. My conclusion was that it was certainly so, and I have not altered my opinion (Croizat, 1981:503 ff.) in a recent review. Here, however there is still space left for me to underscore and to discuss a point of evidence richly deserving a minimum at least of print. I am certain that the text I am to quote from the continuation of the one already introduced has not been pondered as it evidently deserves to by any of my readers.
The text in question reads as follows: “Hence it seems to me Darwin, as it has to any other naturalists that the view of each species having been produced in one area alone, and having subsequently migrated from that area as far as it powers of migration and subsistence under past and present conditions permitted, is the most probable. Undoubtedly cases occur in which we cannot explain how the same species could have passed from one point to the other.
But the geographical and climatic changes, which have certainly occurred within recent geological times, must have rendered discontinuous the formerly contiguous ranges of many species”(emphasis mine).
All in all, then, the theory of Darwin amounts to the following: The “species” draws its “origin”—whatever be the reasons of its birth, in space through time, which Darwin is incapable of formulating in a cogent, logical manner—and next indulges in “migration” using “means of dispersal” peculiar to it. Thus construed and presented, Darwin's world of ideas places the Species in the centre of the Biogeographic stage, and imposes upon the naturalist the obligation of enquiring about the species and its doings in spatial and temporal evolution in terms of origins, migrations and relative means of dispersal.
So much for the Darwinian text first quoted, which stands as such as the plain, undisputable birth certificate of Darwin's own theory of Geographic Distribution, meaning likewise of the “zoophytogeography’ of Simpson, Mayr, Darlington, Gould, etc., and the “dispersalism” that permeates more or less openly an enormous amount of the “biogeography”, however styled, now current.
Passing now to the second text quoted, the student is treated to a substantially different panorama. Here, the “species” moves and acts in space and time essentially in agreement with the Earth, its changes of geography, climate, etc., which determines the modalities of its displacement, transformation, vicariance, etc.
What this apparently unobtrusive change in panorama—be it noticed, forming part of the same Darwinian context—actually means is readily seen referring to a simple example, the very same that was starkly presented to my attention some 40 years ago and ruined on the spot for me the credibility of Darwin as a biogeographer.
When studying the botanical genus Euphorbia in warmer Central Asia, I learned that virtually the same species was found in stark disconnection native at one hand in the mountains of Armenia and the Caucasus, at the other hand on the highest peak, Mt. Morrison, of the island of Taiwan (Formosa). This species, already known to Linne as E. orientalis, I had meantime renamed E. calonesiaca, ex descr., rashly assuming that, given the distance between the two disconnected set of populations, they could not be “specifically” identical.
Trying to solve the conundrum, I did first appeal, naturally, to the “biogeographic” wisdom of Simpson, Mayr and their acolytes. The result judged by plain common sense (common sense, by the way, is always a first rate solver of “scientific” difficulties) was a total fiasco: in the first place, the lore of the gentlemen was short of arguments to settle the direction of migration, if any, west to east (Armenia—Taiwan)”, or vice versa. “Means of dispersal” to effect the “migration” were non-existent: the seed of Euphorbia is not palatable to animals and is wholly short of so called epizoic means of conveyance, etc. In sum, it was immediately evident to me that the “biogeography” of Darwin, Simpson, Mayr, etc., boiled down to a supposedly learned dream. Thus warned, I proceeded on my own to elaborate a Method—by no means a Theory once again—that would return to my satisfaction the answer that the pomp and circumstance of the putative authorities of the day was unable to deliver.
The Method I elaborated is the Panbiogeography. I will lose no time here with it, because some 10,000 published pages, very copious indices, etc., stand at the disposal of naturalists candid enough to enquire. I will here pointedly affirm that had Darwin been the genuis he was not, he would have readily understood that centre of origin, migration, means of distribution, etc., were—as he conceived them—flatus oris, not genuine scientific concepts. The issue truly at stake was thus not to be found in the
Species and Earth are brought into conjunction with cause and effect.
The argument I have just spun to the effect that Darwin would have been very well advised in discarding concepts such as origin, migration, means, etc., will strike a great many readers as outlandish, inconsequential, opinionated against a great genius of biology, etc., etc.
Doctor Ian R. Ball has praised my life-work in a quite substantial manner (see p.50). He praises me personally as a liberator, as the pioneer who has opened new outlets to the future. Is it not curious that my work is extolled by a naturalist in excellent standing as having had the merit of throwing out as but confusing rubbish the very mainstays of the “geographic distribution” of Darwin, Simpson, Mayr, Gould, etc., etc? If Ball be right, what was born by Darwin was not a rational “Theory of Geographic Distribution”, but an unfortunate parody of it, which during a century has contributed to prevent the birth of a genuine science of dispersal.
The enormous damage that the Darwinian centre of origin, migration, means of dispersal, etc. have inflicted upon biology in the vital respect of Space and Time, compare with the quite as enormous damage done to the sciences of the Sky by the notion that to be perfect the celestial orbits must be circular, and the final evidence that the sun revolves around the Earth is afforded by the Sun rising and setting at opposite points of the terrestrial horizon. All of this, whether centre of origin or circular movement is plausible on visual grounds, but properly examined it does not at all prove what the vulgus, learned or not alike, take for granted at first glance.
Evidence to the effect that Mayr, for example, supposedly a great authority on matters of evolution, finally and easily mistook “zoogeo-graphic” appearance with biogeographic substance is scattered all over the pages of the article (1982: 618-620) in which he intends to refute panbiog (rather, what he takes for it most confusedly) in favour of his dispersalism rooted in the classical Darwinian props of centre of origin, migration, means of dispersal, etc.
Mayr writes, for instance, (p. 619): “Actually, even the vicarianists cannot help but admit that distributions over an entire or several continents must have been the result of dispersal”.
Vicarianists, Croizatians, etc., are, in the virtually unintelligible ideas of Mayr the unholy crowd that rebels against Darwin, Simpson, Mayr, Darlington, etc. And for the rest, the gentleman does not explain what he intends as dispersal being distinct from dispersal, but it seems clear that by distribution here he means active migration performed with the ordinary means of locomotion of an animal or plant. This being the case, I venture to ask what could be the biogeographic, scientific meaning and value of the statement that, e.g. Marsupialia, “migrated” in some unknown epoch starting with some hypothetical centre (Patagonia?, Canada?, New Guinea?, Tasmania?, etc.) using their legs as a means of dispersal/distribution? If Mayr does really believe that questions of this academic sort, and the rash of theories, guesses, chatter, etc., they beget indeed stand as a Science of Dispersal, he is mistaken, and squarely places himself outside the field of concrete science.
I will here repeat one more characteristic viewpoint of Mayr. He writes (p. 619): “One would think that Croizat,… would proceed to
provide evidence for the falsity of Darwin's belief that “each species has proceeded from a single birth place”, but one searches in vain either for such a falsification or for a “superior” replacement theory”.
When not illiterate or—I hate the adjective—tetragonous against truth, the author of such a statement as this lacks the professional capacity of correctly judging biogeographical questions. The antidarwinian evidence he claims I have failed to return is contained in a detailed, plain, richly documented form in, for example, (Croizat 1962-4), to the indices and pages of which I refer the reader. The Theory of “Geographic Distribution” of Darwin (which also stands as the cornerstone of the “Zoogeography” of Simpson, Mayr, Darlington, Gould, etc., and all its subproducts) fundamentally rests on notions of centres of origin, migration, means of dispersal, etc., of popular inspiration, wholly incapable therefore of promoting scientific enquiry in reference to all kinds of authentic biogeographic problems.
Present Adress: Entomology Division, DSIR, Private Bag, Auckland, New Zealand.
Biologists only familiar with Croizat's well known books such as Manual of Phytogeography (1952), Panbiogeography (1958), and Space, Time, Form (1964) will be surprised at the extent of Croizat's scientific work as illustrated by this first attempt at a bibliography. This is an interim report, and we have no doubt that many items are yet to be located. Hopefully, workers with direct access to the comprehensive library holdings of the United States and Europe will be able to remedy the defects in our listing, and fill the gaps that must exist.
Croizat is best known for his conceptual and methodological work in the field of biogeography. That his studies in this area were founded on a solid empirical data base involving detailed and original systematic work on a variety of angiospermous families seems to have been little appreciated by his numerous critics. Many of these early studies were crucial to the development of Croizat's panbiogeographic methodology and synthesis, as he himself (e.g. Principia Botanica, Vol. la: 346-347) later acknowledged.
Some commentators (e.g. Ball, 1981, Nature 294: 675-676) have claimed that “Croizat…had little interest in the theory of systematics”. Such comments indicate just how unfamiliar most workers are with Croizat's extensive work in this area. For example, reasonably early in his career (1945e) Croizat published a most interesting analysis of natural versus artificial classification systems, and this was followed by hundreds of pages on this subject in relation to both plant and animal systematics in his later work.
In the light of Croizat's (1982) comments concerning extensive and unauthorised alterations to his original draft, we have decided not to list the Croizat, Nelson and Rosen paper “Centers of Origin and Related Concepts” published in Systematic Zoology 23:265-287 (1974). We have both studied Croizat's work and in our considered opinion this paper in no way represents discussion of any of Croizat's concepts of methods, beyond a vague and general criticism of Darwinian biogeography, that is of course not unique to the panbiogeographic method. Additional support for our decision to omit this paper comes from comments by Dr M. T. Ghiselin, who was Review Editor of Systematic Zoology for 1974 and 1975. Ghiselin (in litt.) writes:
“It does not suprise me that Croizat is unhappy about the paper, nor that it poorly represents Croizat's views. I was to some extent privy to the publication of the paper…”
MJH is pleased to acknowledge the friendly and efficient assistance of the staff of the Otago University Science Library, in particular that of Philip Kidd, Inger Gledhill, Greta Bevan and Barbara Smith. He would
Cactus gardens on window sills. Cactus and Succulent J. 2: 327-328.
Cultural notes for the Atlantic Coast. A list of annotated observations on the remarks of Dr K. von Poellnitz concerning A. Berger's classification of succulent A list of annotated observations on the remarks of Dr K. von Poellnitz concerning A. Berger's classification of succulent
Vitis quadrangularis, a succulent vine. Cactus and Succulent J. 3: 137-139.Cactus and Succulent J. 4: 210-213.Euphorbiae. Pt. I Cactus and Succulent J. 4: 291-293.Ceropegia fusca Bolle. Cactus and Succulent J. 4: 227-229.Euphorbiae. Pt. II Cactus and Succulent J. 4:308-310.
A list of annotated observations on the remarks of Dr K. von Poellnitz concerning A. Berger's classification of succulent
Euphorbiae, Pt. III. Cactus and Succulent J. 4:330-334.
Three new Euphorbiae from Madagascar. A new Texan Coryphanta. A plant known as “ Several succulent Notes on tree hardiness.
Nat. Hort. Mag. (Washington) 1934: 96-99.De Euphorbio Antiquorum atque Officinarum, a study of succulent Euphorbiae long known in cultivation. New York. 127 + v pp.Torreya 34:15-16.Euphorbia cactus” (Euphorbia conspicua. N. E. Brown). Cactus and Succulent J.: 523-524.Euphorbiae of the west coast of Africa. Cactus and Succulent J. 5: 582-584.Euphorbia ramipressa. Cactus and Succulent J. 6:78-79.Nat. Hort. Mag. (Washington) Oct. 1934:356-359.
Review of Two new species of
Euphorbia sudanica A. Chev., and Euphorbia trapaefolia A. Chev. Desert Plant Life 7:139-141.“Succulent Plants” by H. Jacobsen. Desert Plant Life 7:120.Tilia from Southern China. Sinensia 6:656-663.
The rare trees and shrubs of Kissena Park, Flushing, Long Island, New York. On the classification of Notes on Where does Lindens in the city of New York and its vicinity. An interesting oak in New York City with brief notes on
Brooklyn Botanic Garden Leaflets, ser. 24, no. 3-5. 11pp.Euphorbia. I. How important is the cyathium? Bull. Torrey Bot. Club 63: 525-531.Elaeophorbia with the description of Elaeophorbia Hiernii sp. nov. Desert Plant Life 8: 102-103.Euphorbia lactea come from? Desert Plant Life 8: 116.J. New York Botanical Garden 37:225-231.Quercus richteri Baen. Torreya 36:139-142.
A noteworthy plant, On the prickles and thorns of Di alcune osservazioni suggerite dalla classificazione corrente del genere An early Tertiary relict in Malaya, On the classification of Une nouvelle espèce de Is Oriental plants in New York City.
Tithymalus or Pedilanthus? Nomenclatural considerations, notes, new names and combinations. Amer. J. Bot. 24: 701-704.Chamaesyce. In O. Degener (Ed.) Flora Hawaiiensis. Family 190. 12 pp. Privately published.Euphorbia epiphylloides Kurz. Desert Plant Life 9: 40-41.Euphorbia teke. Desert Plant Life. 9:66.Euphorbia. Desert Plant Life 9:127-129, 132, 134.Euphorbia L. Revista Argent. Agron. 4: 222-237.Euphorbia ridleyi nom. nov., descr. emend. (E. synadenium Ridl.) and its position in the Linnean genus. Gard. Bull. Straits Settlements 9:145-151.Euphorbia. II. How should the cyathium be interpreted? Bull. Torrey Bot. Club 64:523-536.Kalanchoe du Mozambique. Bull. Jard. Bot. État Bruxelles 14:363-366.Tilia americana L. valid? Torreya 37: 55-57.J. New York Bot. Gard. 38: 62-64.Acer japonicum var. parsonsii Hort. (Veitch & Sons) ex Schwerin, an invalid trinomial. Bull. Fan Memorial Institute of Biology (Botany) (Peiping) 7: 179-200.Euphorbia glaucescens Willd.: an obscure species from British India. J. Botany (April 1937): 105-108.
Mapping the arboretum. A misinterpreted Formosan species, Notes on Chinese Euphorbiaceae. Seven binomials proposed as nomina ambigua. Notes on Euphorbiaceae, with a new genus and a new subtribe of the Euphorbieae. Philippine J. Sci. 64: 397-409 + 1 plate. Glands of Euphorbiaceae and of Euphorbiées Africaines nouvelles ou peu connues: Identifying the lindens Op. cit. 67(4): 7-8. Citation not known. Op. cit. 67(8): 5-6. Op. cit. 67(10): 7-8. Op. cit. 67(12): 7-8. Op. cit. 68(2): 7-8. Op. cit. 68(4): 7-8.
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Une nouvelle sous-famille des Olacacees au Bresil. An interpretation of Identifying woody plants in winter. (Pt. 1). Identifying woody plants in winter. (Pt. 2). Op. cit. 70(10): 7-8, 23. Identifying woody plants in winter. (Pt. 3). Op. cit. 70(12): 5-6.
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On the origin and publication of the name A new species of Crotonfrom Colombia. Notes on Indian Euphorbiaceae: A comment on current notions concerning the leaf, stipule and budscale of the angiosperms. Eight new species of Leguminosae from southeastern China. (Written by F. P. Metcalf with illustrations by Croizat.) Thirty-five new species of American Notes on the Dilleniaceae and their allies: Austrobaileyeae subfam. nov. New and critical Euphorbiaceae form Eastern Tropical Asia. A significant new species from New Guinea: On the phylogeny of the Euphorbiaceae and some of their presumed allies. Critical notes on some Formosan Euphorbiaceae (I). Critical notes on some Formosan Euphorbiaceae (II). Notes on new and critical Far Eastern Euphorbiaceae Identifying woody plants in winter. (Pt. 4). Ameris. Identifying woody plants in winter. (Pt. 5). Op. cit. 71(4):9-10. Identifying woody plants in winter. (Pt. 6). Op. cit. 71(6):8-9. Identifying woody plants in winter. (Pt. 7). Op. cit. 71(9):9-10. Identifying woody plants in winter. (Pt. 8). Op. cit. 71(11):9-10. Identifying woody plants in winter. (Pt. 9). Op. cit. 72(12):7-8. Notebook records of leaves. Op. cit. 72(6): 11. Merrill, E. D. A new species of
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On the systematic position of The Chinese and Japanese species of A discussion of new and critical synonymy. The tribe Plukenetiinae of the Euphorbiaceae in eastern tropical Asia. Preliminaries for the study of Argentine and Uruguayan species of Notes on the Euphorbiaceae II. On methods and experiments. Comments on Far Eastern Euphorbiaceae A further comment on stability in nomenclature. Euphorbiaceae and Sapindaceae. Confusion in vibarnums. Identifying elms in winter. Op. cit. 73(8): 7-9. Review of Note sur
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Notes on the Euphorbiaceae III. New and critical Euphorbiaceae chiefly from the southern United States. Peculiarities of the inflorescence in the Euphorbiaceae. New species of Something about nomenclature rules. New combinations and notes under Is What is a cephalium? Las especies sudamericanas del genero On certain Euphorbiaceae from the tropical Far East. A study of New species of New and critical Euphorbiaceae from the tropical Far East. On The Novelties in Chinese Euphorbiaceae Euphorbiaceae Amoenitates cactologicae. Identifying trees in winter. Identifying maples in winter. Op. cit. 75(13):5-6, 9. Identification of Japanese maples. Op. cit. 76(9):5-7. Paradichlorobenzene is worth knowing.
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A checklist of Colombian and presumed Colombian Cactaceae. Euphorbiaceae novae vel criticae Colombianae, II. Euphorbiaceae novae vel criticae Colombianae, III. Euphorbiaceae novae vel criticae Colombianae, IV. One old and two new species of Three new Amazonian species of New Euphorbiaceae from the island of Mauritius. The publication of A study of the genus A study of the genus A study of the genus A study of the genus A study of the genus A study of the genus A study of the genus A study of the genus Bibliographical notes on the Euphorbiaceae. The homonym question. Additions to the genus Notes on Fijian Euphorbiaceae. Fruit characteristics in rose family. Fruit characteristics in rose family. Part II Op. cit. December 15:7-10. Note sul genere
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A study in the Celastraceae, Siphonodonoideae subf. nov. Una neuva especie de Cactaceas. Nociones sobre las Euforbiaceas de Venezuela. I. Plant observations in Venezuela.
Trochodendron, Tetracentron, and their meaning in phylogeny. Bull. Torrey Bot. Club. 74: 60-76.Euphorbia maculata L. Bull. Torrey Bot. Club 74: 153-155.Lilloa 13: 31-43.Bol. Soc. Venezolana Cienc. Nat. 11: 75-78. (with F. Tamayo).Bol. Soc. Venezolana Cienc. Nat. 11: 79-84.Euphorbia intercedens Podp., a homonym. Amer. Midl. Nat. 37(3): 801-802.Amer. Nurseryman. Nov 1 1947: 11, 53.
The inflorescence of Zea mays a restatement. A new variety
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Una neuva Euforbiacea Venezolana. Una neuva especie Venezolana de Une biographie peu connu de Hipólito Ruiz. Rafinesque: a concrete case. On the Cactaceae; Where north meets south.
Lilloa 17:1-4. (with F. Tamayo.).Drosera L. Lilloa 17: 175-177 (with F. Tamayo).Raputia larensis Tamayo & Croizat sp. nov. Rutacearum. Lilloa 17:223-226. (with F. Tamayo).Lilloa 18: 295-329.Archivio Bot. Biogeogr. Ital. 24 (3rd ser., vol. 8): 169-184. (As “Henricus Quatre”.)Österr. Bot. Zeitschr. 95:497-480.Amer. Nurseryman June 1: 36-38.
Cactaceas nuevas de Venezuela.
Novedades Cientificas. (Cont. Ocas. Mus. Hist. Nat. La Salle, Caracas) Ser. Botanical : 1-4+1 plate.
Pritzel's The status of
Specimen Bibliographiae Botanicae. Chron. Bot. 12: 134-139.Stenocactus “Berger’. Chron. Bot. 12: 165-166. (By L. Cutak, with contributions from Croizat.)
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On nomenclature: the “type-method”. Croizat's review of van Steenis' review of Croizat's “Manual of Phytogeography” 1952.
Taxon 2: 105-107, 124-130.Arch. Bot. Biogeogr. Ital. 29: 367-372.
Una neuva especie Colombiana de La faja xerófila del estado Mérida.
Croton. Mutisia (Acta Bot. Colombiana) 21: 7.Universitas Emeritensis (Revista de la Universidad de los Andes) 1: 100-106.
An essay on the biogeographic thinking of J. C. Willis. Riassunto “Panbiogeografico” (1). Orquideas, aves y comentarios sobre su biogeografia. La Panbiogeographie.
Panbiogeography or An Introductory Synthesis of Zoogeography, Phytogeography, Geology; with notes on evolution, systematics, ecology, anthropology, etc. Vol. 1—The New World. Vol. 2—The Old World. (Bound as 3 vols.). i-xxxi, 2755 pp. Published by the Author, Caracas.Arch. Bot. Biogeogr. Ital. 34:90-116.Arch. Bot. Biogeogr. Ital. 34: 185-198.Mem. Soc. Cienc. Nat. La Salle, Caracas 18:136-146.Rev. Gen. Sci. 65: 367-376.
Riassunto “Panbiogeografico” (2). Riassunto “Panbiogeografico” (3). A note on the origin of
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Typification of On the age of the floras of Fray Jorge and Talinay in Chile. Les Hépatiques par devers la biogéographie. mondiale. De la méthode en Panbiogéographie.
Euphorbia maculata L. A restatement and a conclusion Webbia 17: 187-205.Rev Univ. (Univ. Catól. Chile): 57-61.Rev. Bryol. Lichénol. 31: 5-22.Arch. Bot. Biogeogr. Ital. 38: 82-104.
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An introduction to the subgeneric classification of On approaching the subgeneric classification of Cenni sulla panbiogeografia delle Isole Canarie.
Euphorbia L. with stress on the South African and Malagasy species. I. Webbia 20: 573-706.Euphorbia peplidion and E. tetrapora. Southwest. Nat. 10:241-247.Atti Ist. Bot. Univ. Lab. Crittogam. Pavia ser. 6, 1: 53-98.
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Eucalyptus. Trop. Ecol. 8: 30-66.Euphorbia lutzenbergeriana and E. lagunillarum. Cactus and Succulent J. 39: 142-144.Euphorbia, L., with stress on the South African and Malagasy species. II. Webbia 22: 83-202.Cactus 88: 33-37.
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