The Vegetation of New Zealand
Chapter III. — The Autecology of the Lowland Plants
The Autecology of the Lowland Plants.
Here, unless stated otherwise, only the 559 species of spermophytes and pteridophytes which are confined to the lowlands and lower hills are dealt with, since their autecology should reflect more closely the ecological conditions than would that of the total lowland-lower hills' flora embracing, as it does, many species common on the high mountains.
There are 87 species of trees of which 4 are very tall1, 7 tall, 14 of medium height and 62 of low stature, but at least 39 are epharmonically shrubs and in some 10 cases it is a matter of opinion merely whether they should be classed as such or as trees; nearly all are evergreen, only 7 species being deciduous or semi-deciduous; perhaps 9 may be considered semi-xerophytes.
The following are the life-forms and the number of species to each: — Tuft-trees 10 (tree-ferns 7), canopy-trees 34, bushy-trees 26, fastigiate tree 1, araliad-form 5, leafless juncoid 5, rhododendron-form 6.
1 1) Few accurate measurements are available. For Agathis, trees exceeding 30 m. are common and Cheeseman states it may reach 51 m. (1914: 2 for Plate 84). Dacrydium cupressinum and Podocarpus dacrydioides not infrequently reach more than 30 m., and a tree of the latter measured by E. P. Turner was nearly 60 m. high.
Regarding the tree trunks those of no less than 50 species rarely exceed 30 cm. diam., and in some instances are much less; those of 18 species range from 30 to 60 cm. or rather more; and those of 10 species generally exceed 90 cm., 9 of them having excessively massive trunks1
In some species the base of the trunk is frequently more or less swollen and buttressed2 In tall and medium-sized trees the trunk is frequently unbranched for about two-thirds the height of the tree, a condition arising through suppression of the early branches owing to the close growth of the saplings and their competitors. In the greater part of the species the bark is thin, or fairly so, but in about 18 species it is 12 mm. or more in thickness.
The degree of density and of spread of the tree-crowns is largely a matter of environment. A very considerable proportion are dense and rounded while but few have really far-spreading branches. Podocarpus dacrydioides has a very sparse, narrow crown, small out of all proportion to the size of the tree. Knightia excelsa is almost as fastigiate as the Lombardy poplar and it shows up distinct from the general forest-mass. The head of Metrosideros robusta, though rounded and somewhat wide-spreading, is not dense owing to the leafy portion of each branch not intermingling.
1 1) The diameter of the trunk, as also the height of the tree, is partly a matter of epharmony. Thus the podocarps of the Volcanic Plateau are, as a rule, of considerably lower stature than those of the Western district, but of far greater girth. In Stewart Island the average both for height and diameter of trunk reaches the minimum. Agathis at times possesses by far the most massive trunk of any New Zealand forest-tree, a diameter of 7.2 m. having been recorded, but trunks of this character are usually hollow, but a diameter of from 1.5 to 3 m. is not uncommon. A diameter of 1.5 m. is met with in Podocarpus dacrydioides (Fig. 24) and Dacrydium cupressinum and the trunk of P. totara attains still greater dimensions (Fig. 25.) Nor are massive trunks confined to the Coniferae, e. g., that of Laurelia novae-zelandiae may reach 1.8 m. diam., and 1.2 m. to 1.5 m. is not an unusual diameter for the trunk of Nothofagus fusca or N. truncata.
2 True plank-buttresses occur in Laurelia novae-zelandiae (1.8 m. high by 12.5 cm. thick) and in the lowland-high mountain Nothofagus fusca and N. Menziesii, and the low-land-lower hills N. truncata, and rounded buttresses in the case of several trees, particularly Podocarpus dacrydioides and Beilschmiedia tawa.
3 Yeates (1924: 121–124) has shown that the nodules are lateral roots the apical growth of which has been checked and that they are occupied by a fungus, while, "out of several hundreds of nodules examined representing about twenty species … only one nodule could definitely be said to contain bacteria similar to those figured by Spratt and McLuckie." The tubercle-bearing plants constantly grow side by side with vigorous trees of species unprovided with tubercles. Nor is the growth of Agathis and the podocarps at its maximum under wet forest conditions, but rather in good, well-drained garden soil, so that explanations of the presence of nodules based on their being "adaptations" seem far fetched.
1 1) Extending from the plank-buttresses for several (perhaps many) metres on the wet forest-floor are the raised, laterally-flattened roots of Laurelia from which solid upright broad or conical projections ± 12 cm. high, usually covered with bryophytes, project out of the substratum of shallow water or soft mud.
2 In Eugenia there are small cylindrical root-branches — presumably pneumatophores — first described by Cheeseman (1920: 9, 10). Apparently from what -I have seen of these organs, they show every transition from ordinary roots which enter the ground to those described by the above-named botanist as erect; those horizontal in direction are a common feature.
3 Figures as usually supplied are more or less misleading, since nothing is said as to the environment of the tree of which the measurement is given and on this all depends. The following in this paragraph are a selection from a number of trees the annual rings of which were accurately counted by H. B. Kirk (to each the age and diameter is given): — Libocedrus plumosa, 252 years, 30.2 cm. diam; 143 years, 32.2 cm. diam. Agathis australis, 238 years, 39.4 cm. diam Dacrydium, Kirkii, 373 years, 44.0 cm. diam. D. Colensoi, 479 years, 45.8 cm. diam.; 400 years, 43.6 cm. diam.; 109 years, 21.3 cm. diam.; 101 years, 15.5 cm. diam. D. cupressinum, 374 years, 44.6 cm. diam.; 258 years, 472 cm. diam.; 315 years, 47.8 cm. diam. Podocarpus totara, 425 years, 111.6 cm. diam.; 343 years, 41.4 diam. The various species of Nothofagus grow more rapidly than any other tall tree and the following measurements, taken from an open stand of yung trees, give some idea of rate of growth: — 46 years old, 25 m. high, 45 cm. diam. (breast high); 39 years, 20 m., 41 cm.; 46 years, 24 m., 36 cm.; 51 years, 24.9 cm., 35 cm. The following are rates of growth of certain young trees within Leptospermum scoparium shrubland:—Agathis australis, 12 years old, 35 cm. high, 8 mm. diam.; 16 years, 1.5 m., 15 mm.; 32 years, 3 m., 20 mm.; 8 years, 27.5 cm., 4 mm.: Phyllocladus trichomanoides, 26 years, 2.1 m., 14 mm.; 22 years, 1.5 m., 10 mm.; 15 years, 1.3m., 10 mm.; Knightia excelsa 10 years, 2.7 m., 14 mm.
4 Nothofagus cliffortioides (in bright light), 9 years, 3.6 m., 37 mm.; 7 years, 5.4 m., 51 mm.; 11 years, 5.5 m., 60 mm., (in shade alongside the above), 17 years, 1.5 m., 17 mm.; 34 years, 6 m., 58 mm.; Nothofagus Menziesii (in fairly bright light on outskirts of forest) 16 years old, 87 mm. X 70 mm. diam.; (in forest interior), 43 years old, 48 mm. X 47 mm. diam., (in excessive shade within the forest according to G. Simpson and J. S. Thomson), 36 years old, 2 4 m. high, 15.6 mm.; 57 years, 3.6 m., 265 mm.
The leaves of the trees may be characterized as follows: — evergreen 70, deciduous or semi-deciduous 7, compound 19, simple 63, broad 67, narrow 15, very large 10, large 12, medium-sized 29, small 17, very small 14, leafless except in juvenile 5, thin 34, coriaceous 48, glabrous 62, hairy 20 (tomentose beneath 8), waxy beneath 6, glossy 20. Most of the coriaceous-leaved species are not xero-phytes, the stout texture of leaf being rather in relation with the evergreen habit. Myrtus hullata stands almost alone. in its curious reddishbrown broadly-ovate leaves, 2.5 to 5 mm. long, concave beneath, but above, the surface between the veins is raised in blisters, but blistered leaves — a character unknown in those of the parents or in the genus — also occur in some forms of that vast hybrid swarm, X Nothofagus cliffused. With regard to deciduous leaves, those of the species of Edwardsia do not depend upon decrease in temperature but the leaves fall just before blooming takes place and new ones rapidly develop as soon as this is over, but this behaviour is not uniform for all the jordanons.
There are 82 species of shrubs of which 75 are spot-bound, 7 wandering, 46 mesophytes, 36 xerophytes or subxerophytes, 67 evergreen 3 deciduous or semi-deciduous, 12 virtually leafless when adult; while, as for height, 23 are tall (8 epharmonically trees), 34 of medium height and 25 of low stature. Though none pass through a long-persisting juvenile stage, 12 (as early juveniles) have a leaf-form different from that of the adult.
The following are the life-forms of the shrubs and the number of species to each: — erect bushy-shrub 26 (more or less dense 22, open 3, fastigiate 1) divaricating 17 (partly so 3, switch-shrubs 2), straggling 10 (erect 7, semi-prostrate 3), switch-shrubs 8 — excluding the 2 divaricating (erect 7, spreading 1), rhododendron-form 7, ball-like 5 (1 partly so), tuftshrub 3 (ferns 2), mat-form 1, erect creeping and branching 4 (all lycopods), bamboo-form 1.
The branchlets (excluding ferns and Cordyline) may be divided into: moderately-stout 16, stiff or wiry 35, slender or twiggy 28. The bark is in nearly all cases quite thin. The trunk of Blechnum Fraseri varies from about 30 to 70 cm. in height and is not thicker than a moderately stout walking-stick. From its base numerous runners pass off extending horizontally just beneath the surface of the ground and at a distance of some 10 cm. a young plant is produced which develops first a trunk and then runners, so that extensive, dense colonies are formed by vegetative increase alone. The trunk of Todaea barbara is short but massive and thus quite unlike the tall, slender trunk of a typical tree-fern.page 132
Some of the shrubs, especially the xerophytes, root deeply. The species of Hebe readily produce adventitious roots from near the bases of the stems, so that a shallow-rooting mass of roots is formed.
The leaves of the shrubs may be characterized as follows: — compound 5, simple 65, leafy (very small) only in juvenile or wanting 12, broad 50, narrow 20, thin 33, coriaceous 37, glabrous 47, hairy 23 (tomentose 15), and with regard to size 1 is very large, 7 are large, 15 of medium size, 13 small, 34 very small.
c. Herbs and semi-woody plants.
There are 299 species of herbs and semi-woody plants (exclusive of aquatics but including ferns) of which 184 are spot-bound, 115 wandering, 14 hygrophytes, 260 mesophytes, 25 xerophytes, 15 annuals, 284 perennials (semi-woody 25, summer-green 44, evergreen 215); while as for height 34 are very tall, 45 tall, 74 of medium stature, 53 of low stature and 93 either hug the ground or are less than 15 cm. high. No fewer than 65 are pteridophytes and 122 monocotyledons, so that only 37 per cent, are dicotyledons.
The life-forms and the number of species to each are as follows:—(1.) Annuals and biennials 15 consisting of: tufted fern 1, lufted grass 1, matform 2 (rooting 1), erect-branching 9, semi-erect 2. (2.) Perennials 284 consisting of: (a.) semi-woody 25, which include (a.) wandering 8, consisting of erect-branching 5, rooting-mat 1, rooting-straggling 2, (Β.) spot-bound 17. consisting of ferns with short trunk 7, tufted grass 1, erect rosette-plant 2. erect-branching 6 and procumbent 1; and (b.) herbaceous perennials 259 which include (a.) wandering 107, consisting of: erect creeping and rooting 44. (ferns 28, grass-form 7, rush-form 7, iris-form 1, saprophyte1, erect-branchingcreeping and rooting 6 (all herbs), semi-erect branching creeping and rooting 2 (both herbs), prostrate-branching creeping and rooting 5 (herbs 2, Utriculariaform 3) rooting-mat 50 (ferns 7, rush-form 1, grass-form 1, herbs 41); and (Β.) spot-bound 152, consisting of: erect tufted-form 46 (ferns 21, grassform 10, rush-form 12, iris-form 3), semi-erect tufted-form 2 (all of grassform) tussock-form 27 (grass-form 19, rush-form 8) mat-form 5 (grass 4, rush 1), summergreen bulb-form 2 (both grass-like), earth-orchid form 42. semi-erect branching 5 (all herbs), low rosette-form 7 (all herbs), erect rosette-form 2 (both herbs), erect branching 12 (all herbs) and stragglingbranching 2 (both herbs).
1 1) The saprophyte (Bagnisia Hillii) according to Cheeseman (1909: 141, 142) is found in decaying leaves and humus at the base of Podocarpus dacrydioides. There is a branching, fleshy rhizome 5 to 10 cm. long and 1 to 1.5 mm. thick. Leaves are wanting and the vegetative parts are colourless. One-flowered peduncles, 5 mm. to 15 mm. in length, are given off from the axils of the minute fleshy bracts. The flower is rose-pink and about 1.5 cm. long by 7 mm. broad.
Taking the leaves (19 are leafless) of all the classes of herbs and semiwoody plants together, their characteristics and the number of species to each, are as follows: — compound 72, simple 208, broad 176, narrow 104. coriaceous or fairly thick 76, fleshy or succulent 4, thin 200, glabrous 217. hairy 63 (tomentose 12). As for their relative dimensions 23 are very large, 33 large, 43 of medium size, 71 small and 110 very small.
New Zealand, notwithstanding its wealth of inland waters, possesses remarkably few aquatic vascular plants. Here, though both the purely lowland species and those ascending to the high mountains are dealt with, only 16 come into consideration. Really no line can be drawn between aquatic and swamp plants and the species of Myriophyllum included here could quite well be transferred to the latter class, while several already dealt with as land-plants could come here. But, even were the widest view taken of water-plants the list would number less than thirty.
The 16 species fall into the 2 divisions — free-floating (5 species) and rooting (11 species). The former consists of the highly differentiated Azolla rubra, 2 species of Utricularia (1 with floating shoots ± 60 cm. long) and 2 species of Lemna. The latter are represented by 4 entirely submerged species (rush-form 3, ribbon-form 1), 2 partly submerged with their upper portions extending out of the water (Myriophyllum) and 5 with floating leaves (Potamogeton 3, Callltriche 1, and the rare grass, Amphibromus fluitans).
d. Lianes, epiphytes and parasites.
Here not merely the purely lowland species are dealt with, but all that occur in the lowland-high mountain belt. The New Zealand lianes are of peculiar interest since they are not only numerous and of great physiognomic importance, but many bear the true tropical stamp while the climbing Myrtaceae are autochthonic. The total number of lianes is 45 belonging to 16 families and 22 genera; 11 are scramblers, 12 rootclimbers, 13 winders and 9 tendril-climbers while 29 are woody (27 endemic). and 16 herbaceous or semi-woody (ferns 8).
The scramblers consist of 2 ferns, 1 woody grass, 5 species of Rubus, 1 switch-shrub (Carmichaelia gracilis), Fuchsia perscandens and 1 dimorphic shrub-composite (Helichrysum dimorphum). The least differentiated members of this class are but little removed from many woody plants of the forestinterior which lenghten their internodes considerably and assume a spindling habit. For example, one seeing the bushy-shrub form of Fuchsia perscandens in the open would hardly connect it with the lianoid coils of the same species on the forest floor. Gleichenia microphylla is merely a faculative liane, thanks to it fortuitously possessing plagiotropous pinnae suitable for climbing purposes. So, too, the flexuous stems of the coastal-inland Angelica geniculata, too slender to stand erect, make that species a liane. More page 134lianoid is the rare cupressoid Helichrysum dimorphum with its flexible cordlike, unbranched climbing-stem and its eventual close head of leaf-bearing twigs. But the highest degree of differentiation is shown by the different species of Ruhus, since their leaves, more or less reduced to midribs furnished with hooked prickless, are special climbing organs which cling to anything they touch, and using the shrubs and comparatively low trees of the forest undergrowht as their path upwards, eventually gain the forest canopy where in the bright light they produce flowers and fruit. Their main stem, at first extremely slender, gradually thickens and becomes covered with rough bark while an ultimate diameter of 12 cm. ore more is quite common. The leaves of the scrambling lianes and the number of species for each class are as follows: — compound 8, simple 3, broad 9, narrow 2, coriaceous or thick 7, thin 4, glabrous 8, hairy 3, very large 2, large 4, small 2, very small 3.
The root-climbers consist of 5 ferns, 1 of the Pandanaceae and 6 of the Myrtaceae. They are not confined to trees and shrubs as their hosts but cover the faces of rocks and frequently creep over the ground. In the case of the ferns, it is hardly feasible to separate the climbing from the epiphytic, because many which have no connection with the ground are really climbing epiphytes. Polypodium diversifolium (stem thick, green, fleshy) is equally a ground-herb, a liane and an epiphyte. Blechnum filiforme, Arthropteris tenella, Polypodium pustulatum and P. novae-zelandiae are almost obligate lianes. Freycinetia Banksii and the species of Metrosideros are specially imporant root-climbers. The former has a terete, hard, woody, rigid stem, 2.5 cm. or so diam. fastened to the host by stout roots which pass quite round a slender trunk and finally branching copiously cling most closely to the bark. The leaves are sword-like, 60 cm. or more long, thick coriaceous, glabrous and may quite hide the tree-trunk. The species of Metrosideros have stout, woody climbing stems which ascend the loftiest trees and are at first fastened tightly to the host by numerous aereal roots. Lateral branches are given off freely, which at first soft and fleshy, grow rapidly but put forth no roots until woody, the apical portion being rootless and having only partially developed leaves. The climbing shoots are pressed more or less tightly against the bark, M. perforata being most marked in this regard, the small, thick, roundish leaves pressed tightly against the bark forming typical leaf-mosaics. Finally, in all the species, lateral non-climbing shoots are developed which can bear flowers and fruit, their leaves more or less distinct from the juvenile. The main climbing stem, in the highest-climbing species, eventually lose their roots, are held away from the trunk and increase in thickness attaining, in M. scandens, a diam. of 15 cm.
The winding lianes are represented by 1 fern, 1 lycopod, 6 woody spermophytes and 5 herbs, of which 4 ascend to the forest canopy, 5 are page 135confined to shrubs or low trees and 4 merely climb over tall grasses or at best low shrubs.
The climbing stems are usually quite slender and so can make use of small shrubs and young trees in order to raise themselves in the first instance, but these are frequently killed by the increasing pressure of the winding stem, and the number that thus succumb must be indeed great. Sometimes for many square metres at a time the black stems of Rhipogonum scandens form close entanglements, no trace remaining of the original host-plants.
Lycopodium volubile is an interesting example of the transition of a creeping ground-plant to a-winding-liane by way of a scrambling plant, In the case of Senecio sciadophilus, a true winding Kane, the stems when on the ground put forth long roots in abundance, branch, extend over a considerable area and are, in fact, creeping plants pure and simple. The occasional winding of the root-climber Blechnum filiforme, when the support is specially slender, may be cited also. Rhipogonum scandens at first puts forth a stout, succulent fast-growing stem from its root-stock, sparingly furnished with a few scale-like dark-coloured leaves, but the mature climbingstem gives off non-climbing branches which bear large, green, oblong, coriaceous leaves. Lygodium articulatum forms masses of wiry, slender, brown, extremely tough climbing-stems which wind round one another as well as the branches of the support. These stems are morphologically leafspindles of unlimited growht. A frond thus may attain the great length of 40 m. but frequently the liane is confined to shrubs or low trees. The 2 species of Muehlenbeckia are extremely leafy, M. australis covering low trees with a dense mass of verdure. The stems of the 2 species of Parsonsia are slender and pliant frequently winding not only round the host but round themselves. Both species show most remarkable heterophylly, there being three distinct leaf-forms at different stages of the plant's development.
The adult leaves of the winding lianes are, compound 1, simple 12, thick or coriaceous 4, thin 9, glabrous 10, hairy 4, glossy 2, waxy beneath 1, very small 3, small 7, medium 3 and large 1.
The tendril-climbers include only the 8 species of Clematis and monotypic Tetrapathaea tetrandra (Passiflorac). All are medium-sized lianes with comparatively slender (except Tetrapathaea) much-branching stems and they usually drape low trees and shrubs. Tetrapathaea is in habit and appearance very similar to Parsonsia heterophylla forming dense masses of flexible, slender branches bearing abundant dark-green, glossy, somewhat coriaceuos, ovate-lanceolate, acuminate leaves some 5 cm. long. The tendrils, at first straight and soft, and sligthly curved near their apices, finally become stout and wiry. The species of Clematis form a series of transitions from a thinleaved mesophyte by way of subxerophytes with much-cut reduced leaves to the leafless juncoid xerophytic C. afoliata. The adult leaves are, compound 7, page 136simple 1, coriaceous 2, thin 7, glabrous 6, hairy 2; those of Tetrapathaea are glossy and produced in the greatest abundance.
Here all the epiphytes of the Botanical Region are dealt with. But, as seen when considering the lianes, it is frequently difficult or impossible to decide whether a species is a liane or an epiphyte, so, too, many ground-plants are at times epiphytic especially on trunks of treeferns 1) so that the question of their ecological status becomes a matter of personal opinion. Here the number is kept at a fairly low limit and no plant, unless purely an epiphyte or usually such, is admitted. Strictly an epiphyte is a plant which should be invariably seated upon another. In New Zealand this is true only for certain ferns (mostly Hymenophyllaceae), bryophytes, lichens, algae and a few spermophytes, nearly all the latter being also denizens of rocks, while some are more or less common as ground-plants, e. g. Senecio Kirkii — a candelabra-like shrub 3.6 m. high — is generally terrestial in kauri forest, but epiphytic or rupestral elsewhere. Then there are the species so frequently epiphytes during their youth but which, as the waterbalance fails, send down roots to the ground (Fig. 26) which, enveloping their host, finally grow into a solid mass which functions as a trunk. Well-known examples of this class are Metrosideros robusta — at first a large shrub high up on a lofty tree —, Nothopanax arboreum and Dracophyllwn arboreum (Chathams) both on tree-fern trunks and at times Metrosideros lucida, Griselinia Uttoralis and even the more truly epiphytic G. lucida. Various unexpected terrestial species under the influence of a specially wet climate may occasionally become epiphytes, e. g. Phormium Colensoi, Celmisia major.
Here 50 species (some also dealt with in other classes) belonging to 12 families and 21 genera are considered epiphytes (semi-obligate 32, facultative 13–8 more commonly epiphytes, 5 more commonly ground-plants &c. — partial 5). Their life-forms and the number of species to each are as follows:—filmy ferns 17, tufted ferns 5, creeping ferns 4, iris-like tussocks 3, epiphytic orchid 7 (pseudobulbous 2), shrubs 8 (4 eventually trees), pendulous semi-woody plants 4 (1 frequently erect), prostrate creeping herbs 2.
1 1) This has been carefully investigated by Holloway (1923: 609–616) for the Hymenophyllaceae and he arranges them — taking all the species, some of which are only occasionally epiphytes — as follows together with the number of species in each class: — low epiphytes 10, mid-epiphytes 3, high epiphytes 8. With 2 exceptions the high and mid-epiphytes are also low epiphytes.
The presence of the different life-forms in any forest evidently depends upon the conditions offered, while such are largely a matter of climate. Tree-fern trunks with a thick water-holding mantle of aereal roots offer suitable conditions for the germination of many young trees and shrubs and for the ramification of the slender wiry stems of the Hymenophyllaceae, some seedlings being commoner there than elsewhere and others again equally at home on the forest-floor. The occurrence of many of the spermophytic epiphytes and the larger pteridophytes is bound up with the prior occupation of trunks and branches by epiphytic bryophytes which, in their turn, occupy their epiphytic station thanks to the water-absorbing capacity of their leaves, the sponge-like cushions, mats or masses they build so rapidly and various special water-holding contrivances. In a short time sufficient soil is formed from th decay of the bryophytes to support seedling epiphytes and these, each according to its specific capability, make more soil from their decaying leaves &c. until a surprising quantity of vegetable matter in various stages of decay accumulates on horizontal bougs and forks of branches amply sufficient to support shrubs and herbs of no mean size (Fig. 27.). Leaning trunks are specially favourable for a close epiphytic covering and more favourable still are the irregular bases of Metrosideros robusta (Fig. 28.) and Weinmannia racemosa (Fig. 29.), while the slender branches of small trees are particularly suited for occupation by filmy ferns which in a very wet climate completely surround them, as may more or less xerophytic epiphytes in a drier climate, e. g. Cyclophorus, epiphytic orchids (Fig. 30.).
The epiphytic species of Astelia are ecologically equivalent to the tropical epiphytic Bromeliaceae and like them store up water. Astelia Solandri is a densely-tufted evergreen herb with numerous, ensiform, coriaceous leaves 90 cm. to 1.2 m. long with black, sheathing, fleshy bases covered with a great quantity of long silky hairs which, even in quite dry weather, hold large quantities of water1 The plant forms immense tufted masses high up on the tree-tops, the basal part and earlier leaves decayed and making a usually sopping-wet mass of loose vegetable matter.
1 1) W. R. B. Oliver has most kindly informed me that he has made the discovery that the thick cuticle consists "for the most part of a substance giving a reaction for cellulose" and on its inner side is a layer of cutin. This is pierced by "peculiar organs" consisting of a double row of three or four cells with dense protoplasmic contents" which connect the "outer cellulose absorbent layer of the cuticle, through the cutinised layer, with the epidermal and hypodermal cell layers". Oliver appears to be of the opinion that these organs " have an absorptive function". They occur all over the leaf including the basal portion of the water resevoir. MiΒ M. W. Betts (1920 b: 305) has described something analogous to the above in Astelia Cockaynei, a ground plant of various highmountain communities.
The plant frequently grows on slender perpendicular trunks in what appears an impossible position for a plant so massive and heavy (Fig. 27.).
Pittosporum Kirkii and P. cornifolium are sparsely-branched straggling shrubs with long, flexible branchlets, those of the latter slender and drooping. The leaves of both are coriaceous but those of P. Kirkii are extremely thick. P. cornifolium is occasionally a ground-plant.
Griselinia lucida is at times almost a bushy-tree with thick, furrowed bark. The leaves are obliquely-oblong, thick, coriaceous, bright-green, glossy and 7.5 to 17 cm. long. Although an obligate epiphyte, or rock-plant, it grows luxuriantly in ordinary garden conditions.
The leaves of the epiphytes and the number of species to each may be characterized as follows: — simple 28, compound 22, very large 7, large 10, of medium size 11, small 11, very small 11, coriaceous or thick 31 (fleshy or succulent 6), thin 19.
Here all the New Zealand higher parasites, numbering 16 (11 shrubs, 5 herbs), are dealt with1
1 Phrygilanthus tenuiflorus and P. Raoulii have been seen by no living New Zealand botanist either in situ or as herbarium species; so, though included in the above total, they are excluded from what follows.
2 Loranthus micranthus occurs on various trees and shrubs, including Podocarpus totara, Rubus australis, spp. of Carmichaelia, Melicope simplex, Melicytus ramiflorus, Plagianthus betulinus, spp. of Leptospermum, Dodonaea viscose, and many species of Coprosma. It is also to be found on various introduced trees especially the plum, pear, poplar and laburnum and, according to W. Martin (1924: 27), the elm, willow, apple, rhododendron and "in particular the hawthorn". Tupeia antarctica also has many hosts, e. g. Loranthus micranthus and Elytranthe tetrapetala (both themselves hemi-parasites), Pittosporum eugenioides, P. tenuifolium, Carpodetus serratus, Hoheria Lyallii, Suttonia australis and Shawia paniculata.
The herbaceous parasites-belong to three distinct classes; all are holoparasites. The 3 species of Gastrodia are earth-orchids with slender, straight, erect, unbranched, pale-coloured stems, differing, according to the species, from 30 to 90 cm. or more in height and with extremely long, brittle, fleshy tuberous roots which are parasitic on the roots of certain forest plants.
Dactylanthus Taylori (Balanophorac), according to Cheeseman (1914: text to PL 178), is a root-parasite on Nothofagus, Hedycarya arborea, Pittosporum eugenioides, Schefflera digitata, Nothopanax arboreum, Suttonia australis, Geniostoma ligustrifolium and Coprosma grandifolia. It consists of a fleshy rounded or shapeless tuberous rhizome, rough with wart-like tubercles, which varies in size according to age from 2.5 cm. up to more than 30 cm. diam. During early autum numerous, usually dioecious, highlyfragrant flowers, 5 cm. to 15 cm. high, are given off from the rhizome. H. Hill (1926: 89) describes a certain valley-floor near Opepe (VP.) as "a veritable garden-meadow of Dactylanthus. Opening out, along the dry floor of the valley for a chain or more, appeared hundreds of flowers in clumps."
Cassytha paniculata is a twining, leafless plant having for its host shrubby species of the Auckland gumlands, e. g. Leptospermum scoparium, Pomaderris Edgerleyi, Cassinia amoena &c, to which its slender, very stout, pale stems are attached by means of suckers. These stems pass tightly stretched from plant to plant, so that one may easily trip over them.
e. Persistent juvenile-forms.
There are about 200 species of spermophytes which for a longer or shorter period go through an early stage, or stages, of development markedly different from that of the adult and of these about 165 remain purely juvenile for a considerable period — many years in no few instances — or else this early form is capable of reappearing in some part or other of the plant as a reversion-shoot. Here the phenomenon for New Zealand as a whole is dealt most briefly with.
These 165 species belong to 30 families and 50 genera (10 endemic) and 51 are trees, 82 shrubs, 19 ligneous lianes, 10 herbs and 3 water-plants. Apart from the acquatics, in 106 cases the juvenile is the more mesophytic, page 140in 17 cases the more xerophytic, and in 39 cases there is no appreciable difference.
Perhaps the most noteworthy examples of the phenomenon are those where the persistent juvenile is of a different life-form from the adult and it may be so persistent that in some species a tree may be of one lifeform below and of another above. Sometimes both may flower, or. the juvenile may bloom before the adult stage is reached1 Thus, to all intents and purposes there are two "species" in the one plant. This is more plainly indicated when a flowering juvenile is restricted to a particular habitat which supplies conditions antagonistic to the adult stage, as when the xerophytic divaricating shrubs of the open, Pittosporum divaricatum (Fig. 31.) and Corokia Cotoneaster grow in a moist forest atmosphere they remain at the bushy-shrub (mesophytic) stage.
There is usually no abrupt transition from juvenile to adult but intermediate forms occur, though generally not till the juvenile has reached its full development. Nor can the juvenile always be treated as one distinct entity: on the contrary, there is frequently an early stage — the seedling —, a second stage — the juvenile — and perhaps a third stage — the semijuvenile — which may be long-persisting. The seedling stage is very often amply distinct from the adult but its duration too short for it to be classed as persistent. Such is the case with Hebe in general, e. g. H. Traversii with mesophytic ciliated petioled seedling leaves, but those of the adult sub-xerophytic glabrous and almost sessile; or the toothed seedling leaves of H. buxifolia var. odora; or the thin pinnatifid leaves of the whipcord series. These seedling stages are of such limited duration only because the seedlings occupy habitats unsuitable for their continuance, as shown by the permanence Of the juveniles of the whipcord series of Hebe, of Discaria toumatou, and of the species of Carmichaelia, when grown in moist air.
1 1) The following have been observed blooming when juvenile: — Dacrydium intermedium, D. laxifolium, Podocarpus dacrydioides, Clematis indivisa, Ranunczdus Lyallii, Fittosporum divaricatum, Weinmannia racemosa, W. sylvicola, Pennantia corymbosa, Aristotelia fruticosa, Discaria toumatou, Plagianthus betulinus, Hoheria sexstylosa, Edwardsia microphylla, Nothopanax simplex, N, Edgerleyi, Anisotome filifolia, Dracophyllum arboreum (on reversion-shoots), Parsonsia heterophylla and P. capsularis.
The case of Edwardsia comes naturally at this point. In New Zealand there are at least 4 species. The most common, E. microphylla, goes through a divaricating shrub-form which persists for about 15 years, and then is succeeded by the ordinary deciduous tree-form. But the xerophytic E. prostrata, which comes true from seed, and grows only in a xerophytic habitat, is neither more nor less than a permanent form of juvenile E. microphylla, while E. chathamica is almost of adult "microphylla" form from its commencement, and E. tetraptera never gives a hint of the divaricating shrub stage.
If an epharmonic explanation can be applied to the foregoing and other cases not cited, there are instances where such cannot be urged. For example, there is the remarkable heterophylly in the well-named Parsonsia heterophylla, but even in that case the closely-allied P. capsularis is sometimes a persistent semi-juvenile. Nor can the dimorphy or heterophylly of the following be epharmonically explained: Clematis indivisa, Pseudopanax crassifolium var. unifoliolatum (a contrary example to Knightia), P. ferox and P. lineare. Nor when the life-forms of companion plants are considered is it easy to see why those mesophytic trees with long-persisting xerophytic juvenile forms should possess such developmental differences; so, too, with the small forest-trees and shrubs with juveniles more mesophytic than the adults. In fact, taking a broad view of the question and remembering that certain genera (e. g. Pennantia, Parsonsia) exhibit the phenomenon in New Zealand but do not do so elsewhere, it may perhaps be assumed that the dimorphy dates back to a former period when the species experienced ecological conditions different from those they now experience. Also the question of somatic segregation and hybrid origin must not be overlooked.
1 1) These species include Pseudopanax crassifolium var. unifoliolatum, Pennantia, Plagianthus betulinus, Hoheria angustifolia, H. sexstylosa, Pittosporum patulum, P. Turneri, P obcordatum, Edwardsia microphylla, Helichrysum coralloides and its allies; but it is not safe to be dogmatik, for not enough observations have been made, and in some instances reversion-shoots have been observed considerably above their theoretical limit.
The duration of the juvenile stage differs from that where it lasts for only a few weeks to that persisting for 60 years or more as in the cases of Podocarpus dacrydioides and Elaeocarpus Hookerianus. But in the last examples and many others the rate of development is in harmony with the degree of illumination.
If the species confined to the lowland-lower hills' belt be alone considered omitting the wind-pollinated Gramineae &c, the total number of species dealt with here is 372 of which the flowers of 51 per cent, (orchids omitted) may be considered monoclinous and those of 49 per cent, diclinous. But these figures do not sufficiently emphasize the importance of allogamy for, as well as orchids in general, many hermaphrodite species are dichogamous, but few reliable details as to protandry &c. are available.
About 59 per cent, of the 372 species possess — as judged from the highly unsatisfactory human standpoint — fairly attractive flowers, but those of the remainder are both dull in colour and very small, while some included in "attractive" hardly deserve their place. The attractive flowers are of the following colours to each of which is appended the number of species so coloured: — whites 79, yellows 41, blues and purples 48, reds 24, greens 24 and browns 4. In some cases the colours are combined, especially in the Orchidaceae, and the more brilliant colour, though less in area than the groundwork, is by far the more striking. The most showy flowers occur in the genera Elytranthe, Clematis, Ixerba, Edwardsia, Pennantia, Hoheria, Metrosideros, Hebe, Veronica, Colensoa, Olearia and Senecio. At least 25 per cent, are more or less sweet-scented but I have insufficient details, as also is the case with regard to nectar-flowers. There is no doubt, however, that insects play a most important part in pollinating the lowland plants. Certain of the species are pollinated in part or exclusively by birds and such is probably the case in the following species and genera some, by the bye, not purely lowland: Phormium, Knightia, Clianthus, Edwardsia, Metrosideros scandens, M. lucida, M. robusta and perhaps other species, Fuchsia excorticata, F. perscandens, Vitex and Rhabdothamnus. Cleistogamy page 143has been recorded by G-. M. Thomson in Viola filicaulis, V. Cunninghamii and Melicope simplex.
In the lowland-lower hills' flora there are only about 13 per cent, of the species which bear berries or drupes likely to be eaten by birds. It is specially noteworthy that only 3 of such species are not forest plants, that is the remainder of the forest species have moved along with the forests and not through the agency of birds, though a few may have been carried by other agencies, while the three exceptions are by no means particularly common plants nor do any of them nearly extend throughout both islands. Further, the trifling effect of bird-carriage is shown still more plainly in that only 24 species suitable for such extend throughout both islands, 8 halt near lat. 38° and 18 near lat. 42° while the remainder occur in either one locality or in a very limited area.
Far more efficacious for long-distance travel are those disseminules which adhere to the feathers &c. of birds, e. g. the species of Uncinia (only 1 throughout) and Acaena (several quite local). But other fruits have likewise considerable adhering-power, also the number of all classes of seeds &c. which can be carried in mud by birds is considerable.
With regard to seeds &c. specially suitable for wind-carriage those species with minute disseminules come first (orchids 152 in ail and pteridophytes 101) and of such 39 per cent, occur throughout both islands, but for the orchids alone only 21 per cent. Species provided with a more or less efficient flying apparatus (Clematis, Epilobium, Compositae &c.) number 52 but only 27 per cent, of these occur throughout both islands and some are purely local. From the figures of this paragraph it is again clear that special facilities for travel do comparatively little.
4. Seasonal Changes.
Although there is a distinct response in New Zealand lowland plants to the seasons, yet this is rather the result of long "habit" than of any truly great difference between summer and winter. It is true that in the great majority of species there is a longer or shorter winter resting-period but, at the same time, there are species which find that season eminently suitable for the development of flowers. Thus during winter in such lowland forest as they occur the following are in full bloom: — Dysoxylum spectabile, Nothopanax arboreum, various species of Coprosma especially C. grandifolia, C. robusta and C. spathulata. During August a few northern species come into bloom in the North Auckland forest, especially Edwardsia chathamica, Pittosporum cornifolium, Rhabdothamnus Solandri and Alseuosmia macrophylla. Even on the Canterbury Plain, of Edwardsia microphylla flowers during August. But whenever either of the above species Ed ard a page 144flower just at the time of blossoming the tree loses its leaves only to have them replaced almost immediately. So, too, the deciduous habit of Hoheria sexstylosa and H. angustifolia is correlated not with winter but with blossoming. On the other hand Plagianthus betulinus, which comes into leaf from August to September according to latitude, loses its leaves in the autumn (Fig. 30), as do also either completely or partially Muehlenbeckia australis, M. complexa, Carmichaelia grandiflora, C. angustata, C. odorata, C. gracilis, Aristotelia serrata, Discaria toumatou, Hoheria glabrata, H. Lyallii, Fuchsia excorticata, F. perscandens, F. procumbens (coastal), Olearia virgata, 0. laxiflora, 0. lineata, 0. Hectori, 0. odorata, 0. fragrantissima and Senecio Hectori.
If September, October and November be considered spring; December, January and February summer, and March, April and May autumn, then we may speak of early spring, mid-spring, late spring, early summer, late summer and autumn, as distinct divisions of the growing-season, each distinguished by certain species coming into bloom. According to those divisions the most floriferous period is late spring together with early summer or roughly speaking from the middle of October to the middle of January, the period opening and closing earlier in the north tharl in the south. The following are some of the more characteristic species marking the divisions as above: — 1. (Early spring.) Clematis indivisa, C. foetida. Wintera axillaris, W. colorata, Pittosporum eugenioides, Rubus australis, Melicope ternata, M. simplex, Aristotelia serrata, Leucopogon fasciculatus, Griselinia littoralis, Geniostoma ligustrifolium, Vitex lucens, various species of Coprosma, Olearia rani and Brachyglottis repanda. 2. (Mid-spring.) Agathis australis, various Podocarpaceae, Freycinetia Banksii, Pittosporum tenuifolium, Astelia nervosa, Leptospermum sco\parium, Persoonia toru, Olea Cunninghamli, Olearia Hectori and Senecio Kirkii. 3. (Late spring.) Various species of Nothofagus, Clematis Colensoi, Beilschmiedia tawa, Ixerba brexioides, Carpodetus serratus, Weinmannia racemosa, Pennantia corymbosa, Discaria toumatou, Melicytus ramiflorus, Leptospermum ericoides, Epilobium pallidiflorum, Nothopanax simplex and Olearia arborescens. 4. (Early summer.) Phormium tenax, Cordyline australis, Dianella intermedia, Elytranthe Colensoi, Knightia excelsa, Weinmannia sylvicola, Hoheria angustifolia, Hoheria glabratra, Metrosideros lucida, M. robusta, Gaultheria oppositifolia, Bracophyllum longifolium, Olea montana, Parsonsia heterophylla, Hebe salicifolia, H. angustifolia. 5. (Late summer.) Arundo conspicua, Gahnia xanthocarpa, Astelia Solandri, Rhopalostylis sapida, Hoheria sexstylosa, Nothopanax Edgerleyi, Schefflera digitata, Dracophyllum latifolium, Olearia ilicifolia. (6. Autumn.) Astelia Cunninghamii, A. trinervia, Earina autumnale, Bulbophyllum tuberculatum, Hoheria populnea, Metrosideros scandens, Meryta Sinclairii, Pseudopanax crassifolium, Suttonia australis and Shawia paniculata.
The above account of seasonal changes, and so in other parts of the book, is inadequate and unsatisfactory, since the matter cannot be compressed page 145into so small a compass nor can differences due to latitude and habitat be indicated.
5. Epharmonic modifications.
The more uniform conditions of climate ruling in the lowlands than on the coast or in the high mountains lead to less epharmonic change and to greater uniformity in the associations. All the same, the amount of epharmonic modification is striking enough. Here a few examples must suffice.
Life-forms of identical jordanons within and outside the forest.
Evidently identical jordanons (simple species, simple varieties of a compound species), which occur both within and outside forest, are subject to very different ecological conditions and differences in their life-forms may well be expected. Thus, trees with long unbranched trunks in forest are usually branched to the ground and densely leafy in the open. Certain tall bushyshrubs of the open, in dense forest develop long, liane-like stems which branch only near the apex. In certain forests Coprosma rotundifolia is of true tree-form, but outside it is a strongly divaricating-shrub or sometimes an open cushion. The root-climbing lianes Metrosideros scandens and M. perforata in the open are dense bushy-shrubs (Fig. 33) made up of the ultimate climbing shoots. How plastic are these species is shown by the fact that when the shrub-form comes in contact with a vertical rock or tree-trunk ordinary climbing-shoots provided with roots are soon put forth. Perhaps the most striking case is that of Rubus cissoides, already referred to, which in forest is an ordinary leafy bramble which flowers and fruits freely, but in the open is a globose or flattened, green, bushy mass of flexible stems which never flower, yet any portion, if fairly shaded, will bear flowers. On the contrary, the epharmonically-similar, but not closely related, R. subpauperatus blooms freely when fully exposed to sun and wind. Clematis afoliata, too, is leafy in forest, but flowers best in the open. Examples of a similar character are Pteridium esculentum as a scrambling liane in low Leptospermum forest, Gleichenia microphylla with the segments of the sun-leaves so bent as to form small pouches, but the shade-leaves of the same individual quite flat, and Lycopodium ramulosum sterile in shade but producing sporophylls in bright light.
Effect of a specially moist atmosphere or wet ground.
Various ferns, especially Blechnum fluviatile, B. lanceolatum and Dryopteris pennigera develop short, woody trunks when growing on wet ground in forest. The knees of Laurelia, so common in swamp-forest, are absent when the tree grows under dry conditions. In western Fiord district forest not only is Weinmannia racemosa raised higher than usual above the ground on massive irregular stilt roots (Fig. 29), but Nothofagus Menziesii — "normally" with a solid buttressed base — behaves similarly. Schefflera digitata, which usually has finely-toothed juvenile leaves similar to the adult, in an especially page 146moist forest-atmosphere may have them deeply cut after the manner of juvenile Nothopanax simplex. Phormium tenax growing in dry soil possesses numerous root-hairs, but in very wet soil they are wanting. In the forests of the wettest parts of South Island the leaves of species in general are larger than usual and in some species they are of surprising size, e. g., Rubus australis, Aristotelia serrata, Melicytus ramiflorus, Olearia arborescens.
Life-forms of identical jordanons with different life-histories.
In the case of one and the same jordanon commencing life either as an epiphyte or a ground-plant the adult form may be quite different. Thus, according as Metrosideros robusta commences its career as an epiphyte on a lofty tree or a seedling on the forest-floor, so is the adult, on the one hand, a massive tree with an irregular trunk, but on the other hand, a trunkless bushy-tree. So, too, if Weinmannia racemosa commences life as an epiphyte on a tree-fern, or a seedling upon a fallen tree trunk, it ends as a tall tree but if it commences as a ground-plant it ends as a bushy-tree.
Effect of a specially dry climate.
The ultimate shoots of Hymenanthera alpina, Aristotelia fruticosa and Carmichaelia Petriei become truly spinous; the cushion-form is induced in various semi-woody or shrubby plants of an open habitat; the brown hue of the common tussocks changes to green when they are cultivated in good soil in a forest-climate; fairly tall shrubs are considerably reduced in stature; leaves are greatly reduced in size and attain their maximum thickness; leaves of grasses and sedges flat in moist air are more or less tightly rolled.
The deciduous habit.
Very few of the trees or shrubs are truly deciduous under all circumstances, but the more frosty the climate the stronger the habit. For instance, Fuchsia excorticata, Muehlenbeckia australis, Aristotelia serrata and probably Senecio Hectori fluctuate according to circumstances from truly deciduous to evergreen. Also closely related jordanons may differ in this regard.