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New Zealand Plants and their Story

Chapter IV. — The Natural Shrubberies

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Chapter IV.
The Natural Shrubberies.

Some peculiarities of New Zealand shrubs—The southern heath—the northern heath—Parasitic plants—The central heath—New vegetation since eruption of Tarawera—Adaptations of the heath plants—The subalpine scrub—Shrubby veronicas and daisy-trees—Contrivances of scrub plants to resist drought — Prolonged juvenile forms of New Zealand plants — Some interesting experiments—Various forms of the yellow kowhai.

New Zealand Shrubs in General.

In all gardens where a, speciality is made of our native plants, it is not the trees which are there to be found, but rather the shrubs of the open country. Obviously, these latter are more easy to cultivate than forest plants. But this is not the sole reason: it is special beauty of form or flower that has marked them out as of peculiar merit. In any large garden in the world New Zealand shrubs would deservedly occupy a prominent place. Moreover, they belong, in many instances, to families which have no shrubby representatives in the Old World, whence all our ideas as to botanical form are derived.

The Germander speedwell is a pretty little creeping-plant of English lanes, with bright - blue flowers. It has many relatives in the Old Country, and in both hemispheres; but, with the exception of its New Zealand cousins, one other in Fuegia and a couple or so in Australia and Tasmania, all are herbs, or at best only woody in part. Nearly all the New Zealand speedwells are woody, and vary in habit from plants a few inches tall to forest-trees. Plants of the daisy family are usually herbaceous; but in a few regions, especially oceanic islands, shrubby forms occur, New Zealand being comparatively rich in such forms. Shrubby plants of the heath family are also frequent in our natural shrubberies, and some are of large size and quaint form.

The New Zealand shrubs, too, show some excellent examples of a certain remarkable phenomenon common amongst our plants, but much less frequent in other regions of similar size. This is the passing-through a juvenile form, during the development of the individual, page 51altogether distinct from the adult form, such, a juvenile form frequently persisting for a considerable period of time. Many of the forest-trees have the same curious life-history; but the whole question is briefly dealt with towards the end of this chapter.

There are distinctly two kinds of natural shrubberies in New Zealand —viz., those covering extensive areas with a monotonous, uniform garb, and those occurring mainly in belts composed of many different species of shrubs. The former may be designated "heaths," the latter "scrubs."

All over New Zealand the heaths owe their physiognomy to the dominance of the manuka (Leptospermum scoparium), a plant belonging to the myrtle family, with slender stiff stems, small leaves, and numerous white flowers. These heaths may consist almost entirely of manuka, or other shrubs may be mixed through it. In whatever part of New Zealand it may occur, manuka heath is distinctly a sign of poor land. This shrub is of most catholic tastes. Dry ground or wet, it is all one. It may be found in swamps, knee-deep in water, in sour sphagnum bogs, on wind-swept sandhills, on the faces of dry cliffs, and even on ground impregnated with "chemicals" near boiling springs and mud-volcanoes. Besides the above species, there is also the tree-manuka, L. ericoides, and a species of very limited distribution, L. Sinclairii.

The Southern and the Northern Heaths.

In the South Island the manuka heath, so far as the shrubs go, frequently consists of pure Leptospermum scoparium. Sometimes other shrubs occur in varying quantities, of which Discaria toumatou (the wild-irishman, tumatakuru) and Cassinia fulvida are frequent, while C. Vauvilliersii is not uncommon. The ground-plants vary according to the altitude, soil, and climate. On the Bluff Hill the heath is much richer in species; and specially noteworthy are the large bushes of the mingimingi (Styphelia acerosa), some with abundance of white and others with pink drupes. The bracken fern (Pteridium eseulentum) is a common constituent of heaths, and is frequently the most important plant.

Where the ground is very wet, as on the pakihis of western Nekon, the heath approximates to bog, and would be so reckoned but for the small amount of peat on the surface. The plant-covering consists of various rush-like sedges (Cladium glomeratum, page 52C. teretifolium, C. capillaceum), the bog umbrella-fern, a creeping club-moss, a beautiful gentian (Gentiana Townsoni), Epacris pauciflora, the very rare eyebright (Anagosperma dispermum), some orchids and sundews, and, of course, abundance of manuka.

In the northern part of the North Island the heath is much richer. Amongst its members are the following: A fine daisy-tree (Olearia furfuracea), some plants of the heath family (e.g., Styphelia fasciculata, Dracophyllum Urvilleanum, Epacris pauciflora), a shrubby
Fig. 20.—Pomaderris Edgerleyi, a Heath-plant. North Cape.Lands Department.] [Photo, L. Cockayne.

Fig. 20.—Pomaderris Edgerleyi, a Heath-plant. North Cape.
Lands Department.] [Photo, L. Cockayne.

speedwell (Veronica diosmaefolia), the palm-lily (Cordyline australis), and Coprosma rhamnoides. Smaller shrubs are Pomaderris elliptica (kumarahou), P. phylicaefolia (tauhinu), P. Edgerleyi (fig. 20), and, smaller still, Styphelia Fraseri, a most common plant, with small pungent leaves and edible yellow "berries," which is found in various plant societies, from the sea-level to the alpine region in both Islands.

Beneath the shrubs, or in the open spaces, is a profusion of the graceful club-moss (Lycopodium densum).The climbing umbrella-page 53ferns (Gleichenia circinata and G. dicarpa) form considerable colonies. Everywhere are two rush-like plants (Schoenus brevifolius and S. Tendo) growing amongst the scrub or forming tussocks. The flat-leaved and-stemmed Lepidosperma laterale, another of the sedge family, is frequent in places. The dwarf cabbage-tree (ti-rauriki), (Cordyline pumilio), not looking a little bit like its tall relative, is abundant. Formerly its thick underground stem, incorrectly termed a root, was a favourite food of the Maoris. Careful search will reveal quite a wealth of ground-orchids, all of which are interesting, and some pretty. The climbing sundew (Drosera auriculata), which has pretty pink flowers, and whose tuber beneath the ground allows it to occupy a dry position, is a common plant. The iridaceous plant, turutu (Dianella intermedia), a plant with bright-blue berries, is very common. In the far north of the Auckland Provincial District is the curious, parasitic plant, Cassytha paniculata, which entwines tightly other plants, and stretches its cord-like pale-coloured stems just above the surface of the ground from plant to plant, forming veritable entanglements.

C. paniculata belongs to that remarkable class of plants known as parasites. These are plants which live at the expense of others, to which they are attached. They are provided with special organs for draining the "life-blood" of their unfortunate host. Many, such as the plant in question, have little if any leaf-green, and so are quite incapable of manufacturing their food; but a number, amongst which must be numbered the New Zealand mistletoes (Tupeia, Elytranthe, &c.), are quite able to manufacture the requisite sugars, but nevertheless maintain entirely the parasitic habit. Parasites must not be confused with perching-plants (epiphytes), as is so often done. The latter are lodgers, or guests, who live on the surface of other plants, but do not draw on them for supplies.

The Central Heath of the North Island.

On the pumice-covered tableland towards the centre of the North Island the heath changes its character. Certain of the northern plants are wanting, and some peculiar to the region, or nearly so, appear. Here is that exquisite shrub, Gaultheria oppositifolia, with a profusion of flowers like a glorified lily of the valley. Here also is a peculiar brownish-leaved shrub of the heath family, Dracophyllum subulatum. Manuka is, of course, in abundance as usual.

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In 1886 the eruption of Tarawera led, to the burying of large areas of this plant society by volcanic ash. So thickly did this fall that in some places an actual new land-surface was formed for repopulation. This was of great interest, since opportunities for observing the settlement of a large area of virgin soil under natural conditions are rarely afforded; and in this case there is a clue to what may have taken place long ago in the evolution of the plant-covering of the adjacent country.

Where the heath was but thinly covered, it has reappeared almost in its original form; but where the covering was many feet in depth there is quite a different story. Very shortly after the eruption heavy rain occurred, and the comparatively loose soil was cut into innumerable deep but narrow gullies, with many lateral ones opening into them. The sharp ridges between these gullies are bare, but on their sides wave masses of toetoe grass (Arundo conspicua), a plant not very abundant in the adjacent heath. The "seeds" of this grass would, of course, be brought by the wind. Another common member of the new society is the tutu (Coriaria ruscifolia), its "seeds," of course, having been brought from the plants of the adjacent heath by birds.

Adaptations of the Heath Plants.

Without water, plants cannot exist. It may therefore be expected they have developed many special contrivances to insure the necessary supply. Especially important are those connected with water storage or saving, where there is danger of drought. The clay hills on which the northern heath flourishes, although soaked with water in the winter, become exceedingly dry in the summer, and had the plants no provision for husbanding; their water they would die for lack of moisture.

The leaves of plants serve various purposes. On their undersurfaces usually are many most minute openings, too small by far to be seen with the naked eye, which afford communication between the interior of the leaf and the atmosphere. Through these openings a constant stream of water-vapour issues, and through them, too, a perpetual current of air enters. From the air the plant gets its oxygen for breathing, and its carbonic acid for food purposes, while the water passing away makes room within the plant for a fresh supply charged with nutritive matter drawn from the soil by the roots. If, page 55however, the water-vapour passes from the leaves faster than it can be replaced by the roots, the former will wilt, and in time the plant would die of thirst.

Many contrivances have been evoked to hinder this, and the form of the leaves is in part an expression of the relation of a plant to its water-supply. The heath and the subalpine-scrub plants noted below show many interesting drought-resisting contrivances. Although a leaf loses water principally through its minute pores, some may pass away from the whole leaf-surface. To hinder this the surface is specially thickened, or covered with water-resisting substances, such as wax.

Variations of leaf-form play an important part. Do away with leaves altogether and the case is met. Carmichaelia australis, a northern plant of the pea family, is leafless, but has green, flattened stems, which can function as leaves. The almost leafless wild-irishman (Discaria toumatou) has developed rounded spines which, though they serve likewise as leaves, offer much less surface than would long green stems. The needle-like leaves of the dracophyllums not only present little surface, but they are vertical, and so never feel the full effect of the sun's rays, which together with dry air and high winds have much, effect on the rapidity with which a plant loses water. Pomaderris phylicaefolia reduces its water-losing surface by recurving the edges of its leaves. Olearia furfuracea has a mat of dense hairs on the under-surface of each leaf.

The Subalpine Scrub.

In many places on the high mountains in New Zealand, especially in a part where the rainfall is excessive, upon emerging from the upper forest one is confronted with a formidable natural fence, many chains in breadth, dividing the forest from the meadow land. On certain mountains this belt is absent, or represented by stunted beechtrees or isolated patches of shrubs. The above barrier, composed of a thick and varied growth of shrubs, is designated the "subalpine scrub," and if unprovided with a. track is virtually impenetrable (fig. 21). The shrubs, dense in themselves, have such wiry or rigid branches interlacing into one another that no passage can be made between them. In many places where it is impossible to crawl on one's hands and knees beneath the close mass, the only alternative is to walk upon the top.

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Fig. 21.—Exterior of Subalpine Serub of Mount Anglem, Stewart Island. The large-leaved shrub is Olearia Colensoi; the shrub with erect branches raised slightly above the general level is Dracophyllum longifolium.Lands Department.] [Photo, F. G. Gibbs.

Fig. 21.—Exterior of Subalpine Serub of Mount Anglem, Stewart Island. The large-leaved shrub is Olearia Colensoi; the shrub with erect branches raised slightly above the general level is Dracophyllum longifolium.
Lands Department.] [Photo, F. G. Gibbs.

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At first sight it might seem that such plants would be worthless for garden purposes, and yet they are the very élite of the New Zealand flora. The scrubs of the montane and subalpine river-beds and terraces may also be included here.

These scrubs are the headquarters of the shrubby speedwells (Veronica).Here is Veronica cupressoides, named most fittingly, for no one seeing it for the first time and out of bloom could dream it was not a cypress. Other veronicas met with are — V. buxifolia var. odora, forming shining green bushes, round as a cricket-ball;
Fig. 22.—Olearia macrodonta (probably).[Photo, J. Crosby Smith.

Fig. 22.—Olearia macrodonta (probably).
[Photo, J. Crosby Smith.

V. Traversii, which is of similar habit, but with much less glossy foliage; V. glaucophylla, with sage-green leaves; V. subalpina, an early-blooming species; V. monticola; V. vernicosa: and, indeed, there are dozens of species, many of which strongly resemble one another.
Daisy-shrubs (Olearia) are much in evidence. Common are— O. ilicifolia (the native holly), with musk-scented prickly crinkled leaves; O. macrodonta, somewhat like the above, but with broader and greener leaves (fig. 22); O. nummularifolia (fig. 23), with small page 58
Fig. 23.—Olearia nummularifolia. Subalpine Scrub of Mount Ruapehu.Lands Department.] [Photo, L. Cockayne.

Fig. 23.—Olearia nummularifolia. Subalpine Scrub of Mount Ruapehu.
Lands Department.] [Photo, L. Cockayne.

page 59hard and leathery leaves; O. cymbifolia, similar to the last-mentioned, but with the margins of the leaves much recurved; O. moschata, after the manner of O. nummularifolia, but with larger and paler-coloured leaves; O. nitida, with rather large, glossy leaves, covered on the under-surface with a shining mat of hairs; and O. Colensoi, with thick, rather large leaves, much toothed and covered beneath with a thick mat of white hairs. The remarkable O. lacunosa, with its leaves rather like those of a juvenile lancewood, and its relative O. excorticata, with broader and shorter leaves, are rarer, being confined to the Tararua Mountains in the North Island, and to the northwest and west of the South Island.

Other plants of the daisy family are the cassinias, C. Vauvilliersii and C. albida, this latter being confined to the Kaikoura and neighbouring mountains. To the same family belong also the shrubby groundsels, very common plants of the subalpine scrub, such as Senecio elaeagnifolius, S. Bidwillii, S. cassinioides, and S. Monroi.

The heaths are represented by various species of Dracophyllum and by Archeria Traversii and Gaultheria rupestris, the latter to be recognised by its lily-of-the-valley-like flowers, after the manner of those of G. oppositifolia of the central heath.

Dracophyllum Traversii is a magnificent small tree, with smooth, naked, brown stems, crowned at their extremities with rosettes of stiff, reddish leaves, having long-drawn-out points arching downwards. The subalpine flax (Phormium Cookianum), also a plant of sea-cliffs, is common, as is also, in some localities, one of the speargrasses (Aciphylla Colensoi, var. maxima), a most formidable plant with bayonet-like leaves a yard long.

Little can be said here regarding the adaptations of the members of this society. Like subalpine plants the world over, their surroundings, notwithstanding an abundant rainfall, demand protection against drought. A dense, felt-like mass of hairs is frequently present on the under-surfaces of the leaves. Very leathery leaves are common, and these have a special internal structure to account for their leatheriness, which is of advantage to its possessors. Other adaptations similar to those found in the before-described heath plants are frequently present.

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Prolonged Juvenile Forms of New Zealand Plants.

If the seed of Veronica cupressoides, or of any one of the "whipcord veronicas," as they are aptly designated, be sown, it will quickly germinate and produce a young plant, altogether distinct from its parent. In the old plant the leaves are represented by green scales pressed closely against the stem; they are also thick, and have a peculiar anatomical structure. In the seedling, on the contrary, there are true leaves with, a stalk and blade, which are quite thin and of an anatomical structure absolutely different from that of the adult. In other words, the juvenile and the adult plants might be two different species, each adapted for a quite different mode of life, the adult for an arid climate and the juvenile for a moist forest region.

If we are in a position to carry on our investigations a little further, and to grow some of the seedlings in the open air and others in a glass case so constructed as to always contain air saturated with moisture, the plant in the open will by degrees assume the adult and dry-climate habit, while the other will remain in the juvenile and wet-climate form, not for a week or two merely, but for years; indeed, so long as it is kept in a "moist chamber" it will remain a juvenile plant.

And now for a third experiment. Take a rooted cutting of an adult piece of the veronica, and place it in the moist chamber. After a few weeks its new growth will be of the juvenile form, and juvenile and adult leaves will be on the plant at the same time (fig. 24). Similar experiments with certain of the New Zealand brooms (Carmichaelia) and with the wild-irishman (Discaria toumatou) will lead to a similar result. To inquire into this matter at length would be out of place here, but any general account of New Zealand plant-life would be most incomplete without some reference to this extraordinary phenomenon. A few analogous examples may throw a little light on the subject. Many coprosmas and other shrubs belonging to diverse families* have a curious habit of growth, which makes them outwardly so similar that they are not easy to be distinguished when page 61not in flower or fruit. Their branches are stiff and wiry, and interlace one with the other into a dense mass. A similar form is assumed by trees and shrubs subject to constant wind, especially if combined with a dry station.

If seed of the small-leaved kowhai (Sophora microphylla) be sown, a small and erect plant soon appears. But after a time this puts forth
Fig. 24.—Young Plant of Veronica lycopodioides, which had in part assumed the adult form with scale-leaves, putting forth true leaves in consequence of cultivation in moist air and rather feeble light.[Photo. L. Cockayne.

Fig. 24.—Young Plant of Veronica lycopodioides, which had in part assumed the adult form with scale-leaves, putting forth true leaves in consequence of cultivation in moist air and rather feeble light.
[Photo. L. Cockayne.

zigzag branches, and in a year or two a shrub of dense habit, similar to those mentioned in the last paragraph, results. But it does not remain always such a shrub, for in due course its upper part will grow into a tree, with erect branches and large leaves.
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Sow the seed of Sophora grandiflora. Again comes the small, erect plant; but this is succeeded by no shrubby, dense form: the young plant continues its development without noticeable change until it is fully grown into a tree. Finally, sow seed of Sophora prostrata. Again the upright early seedling appears, then the juvenile shrubby stage, as in S. microphylla; but this time it never develops into a tree, but has this shrub stage as its adult form. Finally, without going into further details, there are about two hundred New Zealand plants which have adult forms differing considerably from the juvenile, many of which can, when fully grown, revert to the early form.

Now, it is held by certain biologists than an organism in its individual development passes, more or less completely, through the stages assumed by the species at various times during its past evolutionary history. If this is so, then juvenile stages represent ancestral stages, and such a plant as the seedling whipcord veronica, with leaves of the above-mentioned experiment, is the ancestor of the present river-terrace V. cupressoides, artificially brought back into the world, and kept so long as the moist-air treatment continues. This treatment, too, shows that the ancestral plant lived in a much moister climate than is New Zealand at the present time. The behaviour of Sophora, too, throws some light on the matter. The very earliest stage would be the ancestral form; but as this is the same in both S. grandiflora and S. microphylla, the former is ancestral from beginning to end of its development, whereas the latter, in its middle stage, exactly resembles S. prostrata.

All this points out that there came a period of drought in New Zealand, or of a climate requiring drought-resisting adaptations. Then certain adaptations against excessive dryness came into being, as in the cases of the shrubby form of Sophora and the adult of Veronica cupressoides. On a more recent change to a wetter climate some individuals of the former genus would grow out of this drought-resisting form, others would remain unchanged; but in the case of the veronica no reversion has taken place, but the "ancestral form" still remains latent.

* The following are some of these shrubs: The weeping-matipo (Suttonia divaricaia), Pittosporum rigidum, the mountain-currant {Aristotelia fruticosa), the wauwaupaku (Nothopanax anomalum), various species of Hymenanthera, and Melicytus micranthus.