The Vegetation of New Zealand
Chapter III. — The Autecology of the High-mountain Plants
The Autecology of the High-mountain Plants.
In this chapter, contrary to the procedure in the first edition of this book, only the 511 species, which never become really members of the truly lowland communities, receive detailed treatment, but brief mention is made of a few other species which play an important part in the high-mountain vegetation.
There are no high-mountain trees which are not at times also shrubs, but 8 may perhaps be considered trees rather than shrubs. Of these "trees" so-called, 7 are evergreen, 1 deciduous and all are low. The following are the life-forms and the number of species to each: — bushy-tree 4 (2 dimorphic), araliad-form 1, tuft-tree 1 and rhododendron-form 2. These trees are not really of much moment in the forests, 3 being rare and local and the remainder absent over wide areas. The really important forest trees are canopy-trees (species of Nothofagus), and, to a lesser degree, the low, pyramidal Libocedrus Bidwillii, and certain low, small-headed podocarps. The remarkable tuft-tree, Dracophyllum Traversii is described in the preceeding chapter. To the tree-composites (rhododendron-form) may be added at least 4 which descend to the lowlands. Generally, these tree-composites have their trunks bent at the base and extending more or less horizontally (Fig. 60). Their outer bark hangs in long strips, as also does that of Libocedrus Bidwillii and Dracophyllum Traversii.
The leaves of the trees may be characterised as follows: simple 7, compound 1, broad 7, narrow 1, large 5, medium 1, small 2, coriaceous 7, thin 1, glabrous 5, hairy 3 (tomentose 2). The leaves of Olearia lacunosa are stiff, thick, narrow and somewhat after the manner of juvenile Pseudopanax crassifolium var. unifoliolatum; there is a prominent midrib on the under-surface from which pass off at a right angle stout lateral veins, so making sunken interspaces which are filled with rusty tomentum.
Here it must again be pointed out that many of the shrubs under conditions favouring rich growth become trees. Also one and the same species frequently assumes epharmonically different life-forms. Here, however, only what is considered the commonest form of a species is considered.
The number of shrubs is 118 of which 95 are spot-bound, 23 wandering, 14 mesophytes, 104 xerophytes or subxerophytes, 109 evergreen, 9 leafless or nearly so, 80 erect, 9 semi-prostrate, 29 prostrate, 6 tall, 36 of medium height, 60 of low stature and 16 of very low stature of which 11 hug the ground.
The following are their life-forms and the number of species to each: — switch-shrub 3, flat-stemmed leafless 2, divaricating 4 (open cushion 1), creeping page 243and rooting 4 (leafless 3), erect bushy 13 (long needle-leaved 2), tufted 2, cushion 13 (open 2), rooting mat 16, turf-making 1, ball-like 13, straggling 15, cupressoid 15 (bushy 4, mat 1, ball-like 1, straggling 1), semi-cupressoid 3 (straggling 3), rhododendron-form 14.
The branchlets of the shrubs may be roughly divided into more or less gtout 22, wiry or stiff 54, slender flexible and twiggy 33 and those much abbreviated of cushions 9. The maximum of rigidity is reached in Corallo-spartium, Carmichaelia Petriei, C. Monroi and Hymenanthera alpina. Wiry, generally slender stems, are characteristic of the divaricating-form; stiff slender stems of the Dracophyllum-form; twiggy stems of Hebe, and fairly stout, rather brittle stems, covered in the younger parts with tomentum, of the shrub-composites. The only truly spinous shrub is Discaria toumatou (also lowland and coastal), but perhaps Carmichaelia Petriei may be considered spinous, and both Hymenanthera alpina and Aristotelia fruticosa produce branchlets spinous at the apex under extreme xerophytic conditions.
Deeply descending roots are a common feature, especially in small, spot-bound shrubs. Obviously, shrubs with creeping rooting stems have less need for long roots. Adventitious roots are readily produced on stems of Hebe, Phyllocladus alpinus, Hoheria glabrata and a few other plants, if they come in contact with the moist ground. The peat-forming cushion-plants give off from their ultimate branchlets many adventitious roots which penetrate the moist peat of the interior of the cushion, so that they are independent of the thick woody, deeply-descending roots for the intaking of water and function mainly in anchoring the plant to the substratum (frequently rock).
The leaves of the high-mountain shrubs may characterized as follows: — simple 109, narrow 20, broad 89, wanting or almost so 9, large 1, medium-sized 8, small 33, very small 67, coriaceous thick or fleshy 100, thin 9, glabrous 73, hairy 36 (tomentose 29). Many species have mesophytic juvenile and more or less xerophytic adult leaves, a distinction strongly marked in the cupressoid form of Hebe and Helichrysum, in Carmichaelia (leafy only when juvenile or in the shade), in Hymenanthera alpina, Aristotelia fruticosa and the vegetable-sheep.
Lianes, epiphytes and parasites.
As these have already been dealt in Section II, Chapter III, along with those of all the altitudinal belts very little need be said here.
Lianes are of little moment in the high-mountain vegetation, Clematis australis alone being confined thereto; but C. marata, Rubus schmidelioides var. coloratus, R. subpauperatus, Muehlenbeckia complexa and Helichrysum dimorphum ascend into the montane belt.
As for epiphytes, there are none of the herbaceous or woody classes, excepting a few ferns, but abundance of mosses, liverworts (some store up water) and lichens. The most remarkable fern — also lowland — is page 244Hymenophyllum Malingii1 which is generally found on Libocedrus Bidwillii (dead trees or decaying parts of living ones, so not really epiphytic), but occurring occasionally on Dacrydium intermedium (Phillips Turner, 1909:3) and perhaps on Podocarpus Hallii.
The only strictly high-mountain woody parasite (and this may be merely dwarfed Korthalsella Lindsayi) is about 5 cm. high and its branches ± 2 mm. broad; it has only been recorded, from one locality (E.) where it is confined to certain shrubs of montane debris-scrub. The fair-sized Elytranthe tetrapetala and E. flavida are abundant on Nothofagus, and Tupeia antarctica occurs on Hoheria Lyallii.
Herbs and semi-woody plants.
These fall into the classes, land-plants and water-plants.
The land-plants number 380 species of which 301 are herbaceous, 79 semi-woody, 13 annuals or biennials, 367 perennials, 39 summergreen, 341 evergreen, 260 spot-bound, 120 wandering, 216 erect, 164 prostrate and 273 xerophytes or subxerophytes, and 107 mesophytes. With regard to stature, 4 are very tall, 6 tall, 42 of medium height, 150 of low stature, 178 of very low stature of which 67 hug the ground. A comparison of the above figures with similar statistics for the lowlands shows some striking differences. For instance, the high mountains have 273 more or less xerophytic species, as compared with but 23 for the lowlands, while species of low and very low stature taken together form 45% of the lowland herbs and semi-woody plants and 86% of those of the high mountains.
1 1) The leaves are narrow, more or less pendulous and 3 to 15 cm. long. They are opaque and reddish or silvery in colour owing to their dense covering of stellate hairs. The leaf is without the ordinary lamina. "The vascular bundle (Holloway, 1923: 597) in all parts of the frond is encircled by thick-walled tissue showing pores in the cell-walls, the outermost limiting layer being thin-walled and protruding as long cylindrical papillae. These latter contain chlorophyl] and function as assimilatory tissue. The papillae are separated from one another by narrow air-spaces, into which the water can be drawn in times of rainfall and held during periods of drought." The stellate hairs already mentioned strongly hinder transpiration and evaporation of the water-film, so that the chlorophyll-containing cells are in contact with water except during that most exceptional occurrence — a prolonged drought.
The leaves of the high-mountain herbs and semi-woody land plants may be characterized as follows: — compound 63, simple 317, broad 260, narrow 120, very large 8, large 9, of medium size 56, small 125, very small 182, thin 122, coriaceous thick or succulent 258, glabrous 243, hairy 137 of wich 56 are tomentose. This matter of hairiness, though frequently considered epharmonic, is largely a definite characteristic of certain families and genera.
Dark-coloured brownish or even blackish leaves are fairly common amongst high-mountain herbs and in those occasionally lowland, e. g. Gunnera prorepens, but I can give no approximate statistics. In some cases, I have proved the colour to be dependant, at any rate in part, on light-intensity, but in other cases this is not the case, for the stain is on the basal sheltered portion of the leaf as in some species of Cotula. Dull reddish or purplish leaves belong to the same category. Glaucous leaves occur in some species, e. g. certain Gramineae, Ranunculaceae, Acaena, Umbelliferae and Compositae.
The subantarctic character of dead vegetative parts remaining attached to the living plant and turning into peat is extremely common amongst New Zealand high-mountain plants and occurs in all degrees of intensity. In the case of Celmisia the rotting leaf-sheats, sopping-wet, are more bulky than the living sheaths that they surround. In the peat-filled cushion-plants the water-holding capacity is very great indeed and the plants are independent of soilwater. Many grasses of tussock-grassland have also a sheathing of dead leaf-sheaths, but these are usually of a drier character than those described above. Living leaves with channelled petioles function in conducting water to the roots as may be seen in certain species of Ourisia and Ranunculus. The great peltate leaves of Ranunculus Lyallii are filled with water after rain, but whether such is absorbed is not known. Ecologically they function in strongly shading the partially buried rhizomes and in preventing occupation of the ground by other plants. Filiform leaves with rolled margins are a characteristic of high-mountain grasses in general. Perhaps the most unusual grass-form is that of Danthonia pungens (Stewart Island), consisting of large patches of tufted culms from a woody root-stock bearing the somewhat distant sub-imbricating leaves which are not erect but stand out obliquely, they vary in length from more than 30 cm. page 246to 5 cm. or even less, and are extremely stiff and coriaceous, thick, palegreen marked with brown, and taper gradually to a sharp truly pungent apex; the blade is equitant, striated and waxy on the upper surface; the leaf-sheaths are long, about 9 mm. broad at the base in large examples, and they persist attached to the plant, slowly rotting, and holding much moisture.
Some of the summergreen and semi-summergreen herbs have rhizomes of considerable size, those of Ranunculus Lyallii being extremely fleshy and frequently 5 cm. diam.
The roots of the class of plants under consideration are, in no small degree, in harmony with the station. Thus extremely long roots are more common in plants of rock, stony debris, tussock-grassland and fell-field than elsewhere. In some cases, roots do not descend deeply but spread laterally, at times, more or less parallel with the surface. The length of roots of different species growing side by side appear to differ considerably, but I have not sufficient observations to go into this important matter in detail.
The water-plants consist only of the submerged, rush-like Isoetes alpinus and the slender stemmed Schizeilema nitens with its very small, thin, shining compound leaves, but a number of herbaceous perennials (e. g. several small Ranunculi, Epilobium macropus, Gunnera dentata, Qnaphalium paludosum) may be considered semi-aquatic, since they occur in shallow streams or where water lies for a long time. Also, many of the lowland aquatics ascend to about 900 m. altitude.
As elsewhere in the book the matter of pollination can receive only the most superficial treatment. Though, as in the other belts, there are but few species of butterflies, their individuals are numerous and there is abundance of Diptera, moths and beetles, so that there is no lack of insects for the purpose of pollination. Furthermore, the frequent high winds must carry the pollen long distances. The plants, in general, bear abundance of seed and seedlings of many — not all — species are in plenty. It is true that seeds are more plentiful some years than others, but climate here is the controlling factor with which both abundance of flowers and insects are correlated.
Taking into account only the 511 truly high-mountain species, and putting aside 81 ferns, Cyperaceae, Gramineae &c., the number dealt with here is 430 species of which the flowers of 57 per cent may be considered monoclinous and of 43 per cent more or less diclinous but these figures are somewhat misleading, since protandry and protogyny are common.
About 80 per cent of the species here being dealt with possess fairly attractive flowers, but those of the remainder are generally both dull in colour and very small. The attractive flowers are of the following colours: — white &c. 266, yellows 53, purple &c. 13 blue 2, red &c. 7, green 2, page 247black 1. The attractive flowers for the most part belong to the Ranunculaceae, Pittosporaceae, Onagraceae, Ericaceae, Epacridaceae, Umbelliferae, Gentianaceae, Thymelaeaceae, Borraginaceae, Scrophulariaceae, Stylidiaceae and Campanulaceae. Many flowers are of a size quite disproportionate to the tiny plants that produce them and in some instances they are in such profusion as to hide the foliage, especially in small cushion plants (Figs. 61, 62). Speaking generally, the floral display of the high-mountains is far more striking than that of the lowlands and the coast. A corrie, one sheet of the dazzling white of Ranunculus Lyallii or Senecio scor-zoneroides, the great mats of Leucogenes Leontopodium on the Tararuas (Fig. 63) far surpassing the famed Swiss edelweiss, or the Mount Egmont herb-field with Ourisia macrophylla and the golden Ranunculus nivicola in full bloom are sights not readily forgotten.
Regarding scent, perhaps 20 per cent of the species are sweet-scented. In some cases the flowers may be inconspicuous, e. g. Stackhousia minima (also lowland) fills the air with delicious fragrance when in full bloom, its tiny yellow flowers close to the ground not visible a first glance.
Taking only the 511 purely high-mountain species less than one per cent have succulent fruits attractive to birds and still fewer have hooked fruits. But about 30 per cent are specially suited for wind-carriage and many more, though possessing no special apparatus, constantly travel considerable distances by aid of the wind; indeed, powerfully as it functions on the coast and in the lowlands, it is of far greater intensity in the high mountains. Wind, undoubtedly is all-powerful in dissemination not merely in carrying anemochores through the air, but in blowing disseminules over the ground. The conditions of fell-field and pumice-steppe in this regard are not unlike those of a dune-area. Light fruits or seeds, such as those of Aciphylla, Anisotome and Hebe will be moved by quite a gentle breeze, but there are none that can withstand a gale that hurls small stones and gravel through the air. Run-off water functions strongly as an agent of dissemination and it must play a far greater part than wind in closed associations. Snow-avalanches are of considerable moment. A number of birds (some of them sea-birds) frequent even the highest mountains and they will transport many seeds &c. which though having no special adaptations for that end may adhere to their feet or plumage, in fact it seems probable that the bird is in large measure responsible for the plant-covering of such an isolated mountain as Mt. Egmont.
4. Seasonal changes.
In the upper subalpine and alpine belts the period of blooming for most species cannot extend much longer than 3 months for any locality page 248and within that space of time many species flower and ripen their fruits. On the contrary, if the whole high-mountain flora be considered, and the montane belt be included, blooming commences in October and extends to a limited extent into the middle of March, and even considerably later. There is no rule for the time of flowering of any wide-spread species, all depends on latitude, altitude, and its relation to sun, shade and the melting of the snow-covering. Thus, the seasonal changes in a snow-filled cirque may be identical with or even later than those at a much greater altitude. The relation of seasonal change to insolation is most marked, e. g. the same species will bloom some weeks earlier in the tussock-grasslands on the east of South Island than on the mountains exposed to the western rain-fall a few kilometres distant. In general, the earlier part of the flowering season is marked by the greater blooming of herbs and semi-woody plants and the later part by that of shrubs and the fruiting of the early flowering herbs &c. During the latter half of March, the whole of April, and to some degree in May, the majority of trees and shrubs are ripening or still carrying their fruit. Almost as soon as the snow has melted, or even before it has quite gone, certain species come into bloom, e. g. Caltha novae-zelandiae, and Ranunculus Buchanani. In what follows, I am indebted for valuable assistance to H. H. Allan, C. E. Christensen, G. Simpson and J. S. Thomson.
Taking first the montane belt of South Island, flowering commences in October, and about the middle of the month the following, amongst others, will be in bloom in the North-eastern district: — Hierochloe redolens, Stellaria gracilenta, Clematis afoliata, Ranunculus multiscapus, Geranium sessiliflorum var. glabrum, Linum monogynum, Coriaria sarmentosa, Discaria toumatou, Viola Cunninghamii, Pimelea prostrata, Angelica montana, Corokia Cotone-aster, Leucopogon Fraseri, Hebe Raoulii, Wahlenbergia albomarginata, Cel-misia longifolia, Helichrysum bellidioides and Senecio bellidioides. In the middle of the same month, Hoheria Lyallii is just coming into leaf (lower subalp. belt, NE.) and Ranunculus Lyallii is just coming above the ground (upper subalp. belt, F.).
During November, blooming commences at a higher altitude, and the following species may be cited for the North-eastern and Eastern districts: — Poa intermedia, P. Lindsayi, Astelia Cockaynei, Chrysobactron Hookeri var. angustifolia, Nothofagus cliffortioides, Colobanthus acicularis, Ranunculus Haastii, R. Monroi, R. Sinclairii, Notothlaspi rosulatum, Oxalis lactea, Aristotelia fruticosa, Pimelea Traversii, Aciphylla Monroi, Ourisia caespitosa.
During December in the lower subalpine belt of the Western district the herb-field is a beautiful natural garden, the following being in bloom: Ranunculus Lyallii, Drapetes Diejfenbachii, Epilobium chloraefolium var. verum, Anisotome Haastii, Ourisia macrocarpa var. calycina, 0. sessiliflora, several species of Euphrasia, Forstera sedifolia, Celmisia coriacea, C. Armstrongii, C. petiolata, and various mat-forming species of the genus.page 249
On the Tararua Mountains during the last week in December Aston noted as blooming (1910a: 13 et sep.), — Phormium Colensoi, Caladenia bifolia, Pimelea Gnidia, Drapetes Dieffenbachii, Aciphylla conspicua, Hebe buxifolia, Forstera Bidwillii, Celmisia hieracifolia, C. spectabilis, Leucogenes Leontopodium and Abrotanella pusilla. On the Waimarino plain (VP.) at the same time as above and earlier, there are blooming in the tussock, tussock-grassland or bog Herpolirion novae-zelandiae, Stackhousia minima, Aciphylla squarrosa, Wahlenbergia albomarginata and Celmisia longifolia.
During January throughout the Southern Alps — but according to their districts — and the North-western district the greater part of the shrubs are in bloom, some having commenced to flower by the end of December, and the subalpine-scrub and low forest is transformed by the wealth of cherry-like blossoms of Hoheria glabatra and the innumerable fragrant snowy flower-heads of the shrub-composites, especially Olearia ilicifolia, 0. lacunosa, 0. nummularifolia, 0. avicenniaefolia and 0. moschata (Mt. Cook southwards). Various species of Hebe are in full bloom, e. g. H. salicifolia var. communis, H. subalpina, H. vernicosa, H. Menziesii, H. macrantha, as also the beautiful Gaultheria rupestris. The herbaceous plants still continue their display, including those already mentioned, but supplemented by others, e. g. Ranunculus Buchanani (SO., F.), R. sericophyllus (W.), R. Simpsonii (F.), R. Godleyanus (W.), Gentiana corymbifera, G. bellidifolia, Ourisia glandulosa (NW., SO., F.), 0. prorepens (F.), 0. macrocarpa var. cordata (F.), Forstera sedifolia var. oculata (F.), Celmisia Dallii (NW.), C. laricifolia, C. sessiliflora, C. argentea (SO.), C. verbascifolia (F., SO.), Leucogenes grandiceps, Cotula pyrethrifolia, Haastia Sinclairii, Senecio scorzoneroides.
On the Volcanic Plateau, at an altitude of 900 to 1800 m there is a considerable floral display, the following characteristic species being in evidence: — Pimelea buxifolia, Epacris alpina, Dracophyllum recurvum, Hebe laevis, Veronica Hookeriana, V. spathulata, Ourisia Colensoi and Euphrasia tricolor. At the same season flowering is at its height on other North Island mountains when, according to locality, these important physiognomic plants are in full bloom: Ranunculus insignis, R. nivicola, Pimelea Gnidia, Gentiana bellidifolia, G. patula, Hebe Astoni, Ourisia macrophylla, Celmisia glandulosa, C. spectabilis, C. hieracifolia, Helichrysum alpinum, Leucogenes Leontopodium and Cassinia Vauvilliersii. By the middle of January, the vegetation of Mt. Anglem (Stewart Island) is quite as much advanced as in the north, owing probably to its lower altitude and the insular character of the climate. Quite 80 per cent of the florula is in bloom including Chrysobactron Gibbsii, Aciphylla Traillii, Dracophyllum rosmarinifolium, Hebe Laingii, Celmisia argentea and C. linearis.
During February, the floral display of the high mountains continues, the shrubs are at their best in the early part of the month, herbs which at a lower altitude are in fruit are blooming in the alpine belt, page 250so that in one place or another examples can be seen of nearly all the alpine flowers. The seeds of a few species are already ripe, e. g. Uncinia uncinata, Ranunculus Lyallii, R. Buchanani, Epilobium pedunculare, E. glabellum, Anisotome jilifolia, Cyathodes empetrifolia, C. Fraseri, Hebe Raoulii, Raoulia glabra and Cotula pyrethrifolia.
Even so late as the first two weeks of March and, indeed, much later, flowers are still to be seen in certain localities especially where the rainfall is excessive and not of necessity at a particularly high altitude. Amongst these late bloomers are Ranunculus Godleyanus, Carmichaelia grandiflora, most species of Ourisia, several species of Euphrasia, Hebe buxifolia, H. annulata, Celmisia petiolata, C. verbascifolia and Leucogenes grandiceps. But apart from the above and others not cited, nearly all the species of Gentiana are both late and profuse bloomers and their season may extend into April. But long before that, the flowering season is over, and herbs and semi-woody plants have ripened their fruits. The shrubs, however, are mostly laden with fruit and the species of Coprosma, thickly covered with translucent drupes of many hues, are objects of great beauty. On river-beds of the Southern Alps, C. brunnea forms strings of shining beads in every shade of blue. Throughout April and early May, there are still many berries, drupes &c. to be seen, but by June they have nearly all disappeared, Hoheria glabrata, for some time beautiful with autumn colouring, has shed its leaves, dead foliage alone marks the presence of Ranunculus Lyallii and Senecio scorzoneroides, on river-beds the great cushions of Raoulia Haastii are green no longer but of a delightful rich chocolate-brown, and the mats of R. tenuicaulis yellowish-green, pale reddish-brown or grey, the shingle-slip species winter beneath the stones, and the alpine vegetation, some of it now reddish or purplish in colour, is at rest until the melting of the snow and the increasing warmth of spring.
5. Epharmonic modifications.
The high mountains offer greater opportunities for epharmonic change than do either the coastal or the lowland belts, since not only is there a more diverse variety of growing-places but considerable differences in altitude, and consequently in climate, come into play. Here only a few of the more striking cases, or classes of epharmonic modifications, can be dealt with and examples are generally discussed in which the life-form of the epharmone is identical with the permanent form (if there be such a thing) of some other species; for instance an epharmonic cushion of one species as contrasted with a stable cushion of another species. In some cases it is not possible to say without experiment whether a particular form be epharmonic or not. Thus, judging from field observations alone, the common subalpine Astelia of Mount Egmont is apparently A. Cockaynei, yet when grown in my garden side by side with a valid page 251example of that species, it clearly revealed itself an epharmone of A. nervosa var. sylvestris.
As is well known, dwarfing is a most common phenomenon in high-mountain species, increase in altitude and xerophytic conditions favouring low growth. Of particular interest is that class in which tall foresttrees become greatly reduced in stature or are transformed to low shrubs. That lofty lowland forest-tree — frequently more than 30 m. high —, Dacry-dium cupressinum, in the subalpine-scrub of Stewart Island, though still mountaining its trunk and erect habit, is dwarfed to 3.6 or 4.5 m. in height. Libocedrus Bidwillii, growing in the subalpine forest of Mount Egmont, is a low tree about 8 m. high, but on the same mountain, when exposed to the westerly wind, it is only 2 m. high, and denuded of all branches on the windward side. The massive Nothofagus Menziesii frequently 27 m. high with a buttressed trunk 1.5 m. diam., or more, in the subalpine-scrub of the North-western district has become merely a medium-sized, much branched shrub.
As already seen, the prostrate form is eminently characteristic of the high mountains, so that no less than 40 per cent of the 511 true high-mountain species are more or less prostrate. In addition, many shrubs and even some trees are epharmonically prostrate; in fact, it is not feasible in some instances to assign the "normal" either to the prostrate or erect form. Thus, Podocarpus nivalis is a spreading shrub 1.8 m. high in the lowland belt of the Western district and it retains this life-form, though its stature decreases, up to an altitude of about 900 m., yet in the far drier North-eastern and Eastern districts, as a member of the fell-field association, it forms far-spreading, rooting mats. The small forest-tree, Dacrydium Bidwillii, when growing on ancient moraine, spreads for many metres as a more or less circular, prostrate, rooting shrub, and this epharmonic-form which epharmonically grades into the tree-form is actually defined in floras as var. reclinata, while the tree-form receives no mention.
Perhaps the most striking case of all is that of the ubiquitous Leptospermum scoparium, which may be a tree in the lowlands, an erect shrub of subalpine-scrub, or make on boggy ground a veritable turf less than 5 cm. deep, its shoots rooting abundantly. Dracophyllum rosmarinifolium (Stew., F.) under one set of conditions is also a turf-maker, under another set a creeping, rooting shrub, and under a third it builds massive, dense cushions (Fig. 53).
Excessive wind, as can be seen further on in regard to the Denniston plateau, is frequently responsible for the prostrate form, but xerophytic conditions, or sour soil under the high-mountain climate, are likewise potent agents.
This form also is characteristic of the high mountains and occurs in 21 families. It can also be constantly seen in the page 252making, and even the most unlikely forms may become epharmonic cushions. Thus, Aciphylla Traillii — an erect plant some 12 cm. high with thick, rigid, spinous, 3-foliolate leaves 5 cm. or more long — on Table Hill (Stew.) where it grew on a piece of moist open ground, all competitors being absent, had its leaves reduced to rosettes, each 5.5 cm. diam. which pressed close together made a fairly large, dense cushion — a form supposed to be constant ("normal") for Aciphylla Dobsoni. When Helichrysum coralloides — an erect (or sometimes drooping with long shoots) cupressoid-shrub which is confined to rocks — is somewhat more exposed to wind than usual it assumes the cushion-form (Figs. 64, 65). Dacrydium laxifolium, a turf-making bog-plant of the Southern Alps, when growing on the dry pumice of the Volcanic Plateau, becomes a close cushion (Fig. 70). But it has already been shown that the hard, dense cushion of Dracophyllum rosmarinifolium is an ephar-mone and the suspicion arises that many other cushions belong to the same category. For example, nothing could seem less plastic than the cushion-species of Raoulia, yet R. bryoides frequently puts forth shoots with open leaves, and any of these vegetable-sheep, if cultivated in a moist greenhouse, will put forth mesophytic shoots and eventually assume an open habit.
This life-form so characteristic of New Zealand, though apparently quite stable, is frequently plastic to an extreme degree. This is well shown by the behaviour of shrubs of this form common in debris-scrub (especially Pittosporum divaricatum, Aristotelia fruticosa and Corokia Cotoneaster) which, when growing in an adjacent forest are open twiggy mesophytes which in that life-form flower and fruit. Hymenanthera alpina — an extremely rigid divaricating-shrub, so reduced in size as to be an open cushion — behaves similarly, but as a mesophyte it apparently does not flower. Here again come in disturbing features for, in the case of the last-mentioned shrub, one almost of the mat-form and one quite erect have been oberved growing side by side. Also the divaricating form is strongly fixed in the case of Nothopanax anomalum which is hardly altered under forest-conditions.
The occurrence of spines.
1 1) In May 1907 G. Simpson and J. Scott Thomson planted a wild specimen of Carmichaelia Petriei in the open ground, keeping it constantly covered with a bell glass, and by the end of November of the same year this entirely leafless, spinous xerophyte had developed leaves on the old wood. Such a rapid change, there being really only 3 months' growing-period, was quite unexpected.
H. H. Allan (1926:75, 76) has shown that a certain form of Ranunculus, which may be R. Monroi var. dentatus is an epharm-one, since, according to its growing-place, the leaves alter greatly in (1) tomentum — "extremely dense … shaggy, appressed, ferrugineous" — to "reduced to very scant hairs" (2) texture — from "coriaceous" to "thin and membraneous" — (3) size — from 3 to 5 cm. × 2 to 3.5 cm. to 10 to 13 cm. × 8 to 11 cm.; and the scapes from simple or 1-branched to sub-corymbose and much-branched.
The common reduction of leaf-surface through incurving or recurving in grasses and certain Compositae is frequently in harmony with dry conditions, for under a moister environment they are flat. This, in the cases of Olearia cymbifolia and Shawia coriacea, I have proved by experiment. It is possible that Celmisia longifolia Hook. f. (C. gracilenta Hook, f.) and C. graminifolia Hook. f. are epharmones, the one of the other, but in this case the question is complicated through the occurrence of hybrids between C. longifolia and one or more broad-leaved species, e. g. C. Morgani Cheesem. is a mixture of such hybrids, which Cheeseman's (1925:953) statement clearly indicates "C. Morgani is its [C. graminifoliaj nearest ally, but can generally [italics mine] be recognized by its much larger and broader leaves".
The presence of tomentum on the under-surface of a leaf may be epharmonic as in the shade-leaves (non-tornentose) and sun-leaves (tomentose) of any tree of Nothofagus cliffortioides.
Physiognomic of tussock-grassland is the brown or yellowish colour of the tussocks, yet cultivated in a lowland garden in a fairly wet climate the leaves remain green or fairly so all the year round. Relative size and thickness of leaves, as noted for the other belts of vegetation, is also clearly a matter of epharmony, and so too the amount of leafage in so-called leafless woody plants. In the case of cupressoid and phyllocladous shrubs — in eluding Carmichaelia and its allies under this term — leafy shoots are put forth under moist conditions especially when accompanied by dim light.
The assumption of the Kane-form takes place in certain true high-mountain plants. Thus, G. Simpson and J. S. Thomson have noted that when the mat-plants, Celmisia Bonplandii and C. Walkeri grow beneath the shrubs of dense subalpine-scrub their shoots lengthen greatly and extend page 254to the roof of the scrub reaching, at times, a length of more than 1.5 m. The carpet-forming grass, Danthonia australis also climbs over shrubs to a considerable height.