New Zealand Plants and their Story
Chapter III. — The Forests
A priceless possession—Rain-forest climate—The two classes of forests—General characteristics of the mixed forest—Origin of special forest plants—Lianes and epiphytes—Flowers—Fertilisation—New Zealand timbers—The kauri forest—The kahikatea forest—The mixed forest and its distribution— Beech forests.
However little the average New-Zealander may know about the plants of his country, few there are who cannot raise some enthusiasm regarding the "bush," as the forest is everywhere called. To old and young it is a delight—the stately trees; the birds, fearless of man; and, above all, the wealth of ferns appeal to all. But that this forest is a unique production of nature, found in no other land, is not a matter of common knowledge, though truly it has many claims to be considered a priceless possession.
According to the famous plant-geographer, Schimper, New Zealand has a rain-forest climate. That is to say, if no inhibitory conditions existed, one green mantle of trees would cover the whole land. Although this is not the case at present, it was in great part so when the early settlers arrived.
But this great forest was not all of one kind. The need of timber for house-building soon proved that various kinds of trees were more abundant in one locality than in another, and that some were wanting in one forest while plentiful elsewhere. As the trees had in many cases Maori names, the settlers soon learnt—in a rough manner, it is true— something as to the composition of the forests and their distribution. But, as some Maori names are used very loosely, accuracy was quite impossible. In this little book, therefore, although it is written for the non-botanical, the scientific names, which are definite, are used, as well as their more popular equivalents when such exist.
There are two distinct classes of New Zealand forests—viz., those consisting of many different species of trees, and those that are formed of but one kind, or nearly so. To the first category belong, with one or two exceptions, most of the lowland forests, page 26and to the latter the upland and subalpine beech forests and the swamp forests of kahikatea.
Let us consider first the ordinary mixed forests, the "bush" par excellence. These differ so considerably in their composition as really to constitute different societies, but all have much in common.
General Characteristics of the Mixed Forest.
The forest is made up of different layers, if we consider the general level of the foliage. The tall trees form the uppermost layer; the page 27smaller trees and tallest shrubs the second; smaller shrubs, tree-ferns, and juvenile trees the third; and finally comes the forest-floor, with its carpet of mosses, liverworts, and filmy ferns, through which grow the smaller ferns and herbs. A most important feature of the forests is afforded by the climbing-plants, or lianes, as they are often called, which, rope-like, hang from the tree-tops, form an impenetrable tangle, or gracefully entwine the smaller trees and shrubs.
Fig. 9.—The Epiphyte, Astelia salandri, growing on erect trunk of the Taraire (Beilschmiedia tarairi). Waipoua Kauri Forest.
Lands Department.] [Photo, L. Cockayne.
Origin of Special Forest Plants.
The forest also tells us a good deal about the evolution of the wonderful adaptations of certain plants to the conditions it provides. On walking through its interior one cannot fail to notice the subdued light, which is so much less than in the open. Above all things, most plants require sunlight. Without this they cannot manufacture in their leaf laboratories their necessary food from the carbonic acid of the air. In a forest, then, there must be a struggle for the sunlight. The tall trees meet the difficulty by raising their tops high into the heavens. But with the smaller plants it is another matter, and these must either become attuned to a minimum of light, or make some special effort to get their fair share. Consequently, we find a spindling habit of growth in many young forest-trees—long, straight, thin stems, and few lateral branches; "drawn up to the light" is the gardener's phrase.
Carry out this idea a little further, and you have certain plants putting out long shoots, which, too weak to stand alone, lean against other trees for support. Go a little further still, and such long shoots develop certain organs to assist them to cling to the supporting tree. So, by slow degrees, modification after modification arises for the end in view, until the wonderful family of lianes or climbing-plants is evolved, whose roots can enjoy the cool and rich soil of the forest-floor, but whose crowns dispute with the tree-tops for the light of heaven, and under its influence bring forth their flowers, ripen their fruits, and manufacture stores of food within their green leaves.
Lianes may be conveniently divided into scramblers, root climbers, twiners, and tendril climbers, names which speak for themselves. Fuchsia Colensoi, a much more slender plant than the tree-fuchsia page 30(F. excorticata), offers a transition to the scrambling habit, being frequently merely a shrub, and at other times a true liane, its thin shoots being thrust amongst the branches of another tree for their support. Here there is no special differentiation of climbing-organs; but in the various species of Rubus it is different. On their leaf-stalks and midribs these have developed special curved hooks for climbing purposes, which grip so tenaciously whatever they touch that they have earned for these plants the sarcastic term of "lawyer." Frequently the leaf-blades are much reduced in size, and the midribs are elongated, so that the leaf is changed in function, and has become a special climbing-apparatus. In New Zealand there are several species of Rubus, which differ considerably in shape of leaf, size of flower, and colour of fruit, the commonest and the one with the largest leaves and most showy flowers being R. australis. One of the commonest root climbers, which with its leathery, green, sword-like leaves much affects the physiognomy of northern forests, is the kiekie (Freycinetia Banksii), whose fleshy bracts, called "tawhara" by the Maoris, are sweet and edible. The roots fasten the plant very firmly to the support, being given off at right angles or thereabouts to the stiff climbing-stem, and, passing right round the support if slender, finally put forth many rootlets, which are parallel, or nearly so, to the main roots, and close together.
Fig. 11.—The Liane, the Supplejack (Rhipogonum scandens), growing as a member of a taxad forest.
[Photo, L. Cockayne.
The well-known supplejack (Rhipogonum scandens), a plant of the lily family, forms close entanglements in most lowland forests (fig. 11) Originally many of these stems have wound round young trees, which page 33have been strangled to death, while others have broken away from the branch to which they had clung. The two species of Muehlenbeckia, relatives of the common dock, are also twining-plants. They are easily recognised by their soft, green, abundant leaves, and when in fruit by the small black nuts seated on a fleshy and almost transparent cup. Very frequently, as bush boys and girls well know, their rope-like stems hang swaying from the forest-roof, the original support long vanished. Parsonsia heterophylla, a pretty plant producing abundance of small sweet-scented flowers, is another very common twining-liane. It occurs especially on the forest-outskirts, or where the bush has been partially cleared. It and its near relative, P. capsularis, may be recognised by the curious long green fruit, something like a kidney-bean in outward appearance. It is especially remarkable for the diversity of forms assumed by its leaves. These may be arranged into three series—viz., small round, long narrow, and finally moderately broad and of an oblong type. Between the small round and the long narrow are all kinds of transitional forms. One variety of the related P. capsularis never reaches the final adult stage, but produces flowers while in the narrow-leaved condition, and so it may perhaps be considered a fixed juvenile form of Parsonsia heterophylla.
The mange-mange (Lygodium articulatum) is a beautiful climbingfern, whose masses of tough slender stems wound round one another make a substitute for a wire-wove mattress by no means to be despised. The leaf of an ordinary fern consists of a stalk and blade, the continuation of the former being called the midrib. The blade may be divided or undivided; in the former case the divisions may be little leaves, each with its own stalk. In nearly all cases the leaf continues to increase in length for a certain time, when its growth is concluded. There is usually no further increase year after year. But the remarkable fern we are considering (Lygodium) is regulated by no such rule, for its midribs may continue to grow until the leaf is so long as to reach the tops of tall trees. The midrib thus has become a climbing organ, and a leaf many yards in length is different altogether from what one imagines a leaf to be. At regular intervals lateral leaflets, which are also capable, of great extension, are given off from the midrib, one at a time, and distant from each other about 4 in., each being furnished with a very short stalk. Two quite different kinds of leaflets may be page 34noted—those which bear spores,* and those which function as ordinary leaves—but between the two are all kinds of transitional stages, very interesting to observe.
Those beautiful flowering-plants, the clematises, are tendril climbers, the tendrils being modified leaf-stalks. Clematis indivisa is the large white-flowered species; C. hexasepala has also white but smaller flowers; C. Colensoi produces masses of yellow flowers in the spring. It is especially abundant in the Wellington Province. C. afoliata is a curious form which looks rather like a mass of rushes. It has few or no true leaves; but they would be a harm rather than a benefit, for it grows in extremely dry places. All the New Zealand species of Clematis have male and female flowers on separate plants, the male being much the more showy.
The New Zealand passion-flower (Tetrapathaea australis) is another tendril climber. In autumn its orange or red fruits, containing numerous black seeds, are very showy. It is not found everywhere, and does not go farther south than Banks Peninsula.
All the lianes are worthy of the closest study, and not the least interesting point is to observe the differences between the climbing and non-climbing shoots. Also, it is remarkable how certain species, such as some of the lawyers and Metrosideros scandens, are lianes under one set of conditions and virtually shrubs under another. It is interesting, too, to grow this class, of plants from seed, and to observe how the climbing habit is not shown at all, or very little, by the early seedling (fig. 12).
Fig. 12.—On left, Seedling of a finally much-branched Drought-resisting Shrub. On right, Seedling of a Climbing-plant.
[Photo, L. Cockayne.
Fig. 13.—Roots looking like climbing stems descending down trunk of a Rimu (Dacrydium cupressinum) coming from an epiphytic Broadleaf (Griselinia littoralis).
Lands Department.] [Photo, L. Cockayne.
Though many plants are eager to get into the fresh air and sunlight, others are, the reverse, and have developed different adaptations in accord with other aspirations. The interior of a thick forest has an atmosphere charged with vapour not altogether unlike that of a glasshouse. Plants living under such conditions are subject to much the same environment as submerged water-plants, and have developed similar leaves, which are so thin as to be able to absorb any water which may fall upon their surfaces. Such, amongst others, are the filmy ferns (species of Hymenophyllum and Trichomanes), the beautiful crape-fern Todaea superba, and its relative Todaea hymeno phylloides. Plants like these can exist only in a moist atmosphere; the full rays of the sun or a dry atmosphere cause them to shrivel up, and they soon die when removed from their forest home. Many mosses and liverworts also belong to this category, and mimic in their forms the smaller ferns, to which, of course, they bear no relationship.
* A spore is any single cell that becomes free from the parent plant and is capable of developing into a new individual. The spores of ferns are contained in spore-cases, and groups of these make the dots or round patches on the under-surfaces of some of the leaves of ferns.
The Flowers of the Forest.
New Zealand forests are not distinguished for their brilliant flowers. On the contrary, most of our forest blossoms are inconspicuous and of a dull colour. But there are some notable exceptions. The northern and southern ratas (Metrosideros robusta and M. lucida) bear multitudes of crimson blossoms. The yellow kowhai (Sophora grandiflora and S. microphylla) has been fitly termed the New Zealand laburnum. The various species of trees known as lacebark (Hoheria, populnea, H. sexstylosa, and H. angustifolia) are, in their season, dense masses of snowy flowers. Pennantia corymbosa (the kaikomako) vies in its purity with any bridal flower. The putaputaweta (Carpodetus serratus) is a rival of the English may. The tawiri (Ixerba brexioides) of the Auckland upland forest is so showy that the Maoris had a special name, "whakou," for its blooms. The tree-manuka (Leptospermum ericoides), with its multitude of white or pinkish flowers, quite equals the popular Spiraea Thunbergi of gardens.
The heketara (Olearia Cunninghamii) produces multitudes of daisylike flowers in the spring. The wineberry (Aristotelia racemosa, mako-page 38mako) has distinctly pleasing rosy-coloured flowers. The hinau (Elaeocarpus dentatus) has numerous white drooping flowers. The large-flowered clematis (Clematis indivisa, puawhananga) is esteemed by all, and its snowy blossoms are frequently torn from their forest home only to wither.
The Fertilisation of the Flowers.
The methods by which flowers are fertilised are of high interest, and for the past half-century have received much attention. Space permits only a brief mention here.
The majority of flowering-plants have two special organs for purposes of fertilisation, the stamen and the pistil. The former produces a yellow "dust," the pollen; the latter contains within a little chamber* one or more little roundish or oval bodies, the ovules. Each ovule contains in its interior what may be called an "egg." If the pollen falls upon that part of the pistil termed the "stigma" at the right time, a union will eventually take place between some of the essential part of the pollen and the egg. This will lead to the formation of an embryonic plant within the ovule, which, when the embryo—i.e., the little plant with seed-leaves and rudimentary root and stem—is fully developed, is termed the seed.
In some instances the stamens and pistil are close together on the same flower, and pollen and stigma are ready the one for the other at the same time, in which case the flower can fertilise itself. But in a considerable number of instances self-fertilisation is impossible, and the pollen of one flower must be applied to the stigma of another. Such cross-fertilisation, as it is called, has been proved to be beneficial for many plants. A large percentage of New Zealand trees and shrubs have the pollen-bearing flower on the one plant and the ovule-bearing on another. Others again are so constructed that the pollen is ripe before the stigma of the same flower is ready to receive it, or the stigma may in other species be developed before the pollen. In all these cases cross-fertilisation is alone possible. This may take place in two ways: either the wind may carry the pollen from one flower to another, as in the genus Coprosma and in many other cases, page 39or animals may convey it dusted on some part of their bodies. In accomplishing this work, insects play a very important rôle. Birds also fertilise a few New Zealand plants, amongst others the puriri (Vitex lucens) and the waiuatua (Rhabdothamnus Solandri).
This action of insects in fertilising plants has led to a widely spread error in New Zealand, and one is frequently gravely informed that bees change the colours of flowers—"inoculating" is the term used. That is to say, the opinion is held that a bee sucking honey from, say, a white flower can turn it red, or blue, or yellow, as the case may be. Of course, neither a bee nor any other insect can do anything of the kind. If, however, the pollen of one flower is transferred by means of an insect, the wind, or any other agency, to the stigma of a closely related individual, of a different colour, the seed which is eventually produced may give rise to a plant bearing a flower coloured differently to that of the parent plant; or, in other words, a hybrid has been produced. Here, then, is the source of the error in an imperfectly understood truth.
* In the pines the ovules are not enclosed, in a chamber, and there is no stigma. The pollen is conveyed by the wind and deposited on the ovules directly.
New Zealand Forest-trees as Timbers.
The forests are of great commercial importance to the Dominion. Some of the timbers are excellent for house-building, others are used as piles for bridges and sleepers on railways, and some are ornamental and can be used for furniture and general decorative work. The wood of the kauri (Agathis australis) is celebrated the world over, but, alas, it is rapidly being exhausted. There seems, however, every probability, according to the late Mr. H. J. Matthews, that a kauri forest from which the large trees have been cut would in time reproduce itself. With this opinion the writer, from his own observations, is quite in accord. It is unlikely, however, that such restoration would be of commercial importance, since the kauri is a tree of extremely slow growth.
At the same time, it must not be forgotten that forests, apart altogether from their timber value, are of the greatest importance to all countries because they help to conserve and regulate the water-supply—a quite different matter, however, to influencing the rainfall. Thus no forest-growth, whether primeval or secondary, should be destroyed without some strong economic reason. There are thousands of acres fit only for the natural growths now clothing them, and the destruction of these forests would be a fatal mistake.page 40
Fig. 14.—"Gum-climber" at work on trunk of a Kauri (Agathis australis).
Lands Department.] [Photo, L. Cockayne.
An important by-product of the kauri is the resin, known as "gum." This is usually dug out of the ground, covered now by the northern heath, but originally occupied by kauri forest. Trees, also, have incisions made into their bark—a mischievous proceeding, the sap flowing out freely, and soon hardening into resin, which is removed finally by men who climb the trees (fig. 14).
The kahikatea (Podocarpus dacrydioides), the rimu (Dacrydium cupressinum), and the miro (Podocarpus ferrugineus) all afford excellent timber for various purposes, the two latter being confused in many timber-yards. The matai (Podocarpus spicatus) is a fine wood for resisting weather, and is only excelled by the totara (Podocarpus totara) and the Westland pine (Dacrydium Colensoi), the D. westlandicum of the "Forest Flora," and the yellow-pine (D. intermedium).These two last, also, are used largely for railway-sleepers. For fencing-posts the puriri (Vitex luccns), the broadleaf (Griselinia littoralis), and the kowhai are excellent, but the first and last become scarcer daily. It should be quite feasible to raise the kowhai artificially in any quantity, since it germinates readily from seed, and will grow very well in the open. The New Zealand honeysuckle (Knightia excelsa, rewarewa) is one of the handsomest woods in the world. Unfortunately, great quantities are destroyed through settlement—a destruction which should be stopped, if possible.
Other valuable timbers are: The northern rata (Metrosideros robusta), which is extremely hard and useful for wheelwright's work and bridge-building, as well as being an excellent firewood; the various species of Nothofagus, especially N. fusca, yielding a durable and strong building-material, which warps more or less; the pahautea (Libocedrus Bidwillii), a very light wood, of a red colour, out of which canoes have been made; the towai or kamahi (Weinmannia racemosa), yielding an excellent bark for tanning, and a wood both ornamental and strong; the pukatea (Laurelia novae-zelandiae), with pale-brown, soft but strong and tough wood, which has been used for boat-building and furniture; the maire-rau-nui (Olea Cunninghamii), an extremely strong timber.
Fig. 15.—A giant Kauri, 46 ft. in circumference at 6 ft. from ground. Waipoua Kauri Forest.
Lands Department.] [Photo, L. Cockayne.
The Kauri and Kahikatea Forests.
As stated at the beginning of this chapter, New Zealand contains many varieties of forests. Here only some of the more distinct are mentioned.
The kauri forest extends from the north of Auckland Provincial District to almost latitude 38°. It is probably the noblest tree community of temperate regions. The kauri (Agathis australis) (fig. 15) is not a close relation of the Old World pines, but is nearer to the monkey-puzzle family (Araucaria).
A kauri forest by no means consists of that tree alone, for the taraire (Beilschmiedia tarairi)—very handsome, with its rather large leaves, darkish - green above and bluish - white beneath—is often dominant.* The kauris form smaller or larger clumps. The kauri trees themselves are some distance apart, and the spaces between are filled up with a close growth of the huge tussocks of the kaurigrass (Astelia trinervia)—which, of course, is not a grass at all, but belongs to the lily family—and a sedge (Gahnia xanthocarpa), with leaves sharp as a razor; while growing through these are certain shrubs or small trees, especially the aromatic-leaved maireire (Phebalium nudum), the spiderwood (Dracophyllum latifolium), Kirk's groundsel (Senecio Kirkii), bearing in its season white daisy-like blossoms, and the silver tree-fern (Cyathea dealbata).Where the undergrowth is more scanty the stately kauris appear in all their grandeur, their huge grey, shining, columnar trunks rising up 60 ft. and may be 80 ft. without a branch (fig. 16), and dwarfing altogether the other trees.
High above the general forest-roof tower the great spreading branches, themselves equalling forest-trees in size. At the base of each tree is a pyramidal mound of humus caused by the shedding of the bark. Common in the kauri forest is the fantastic and irregular trunk of the rata (Metrosideros robusta) (fig. 17), its base covered with sheets of translucent kidney-ferns (Trichomanes reniforme).page 44
Fig. 16.—Interior of portion of Waipoua Kauri Forest, where the Kauris are abundant.
Lands Department.] [Photo, L. Cockayne.
Seen from without, a kauri forest is equally remarkable. The spreading heads of the kauris rise so high above the general forest-roof that it looks as if one forest were superimposed upon another. Very frequently there is found in the undergrowth a miniature tree-fern (Blechnum Fraseri), which has a very slender trunk 1 in. or less in diameter—not thicker, indeed, than a stout walking-stick—and rarely more than 3 ft. tall, and which spreads into large colonies by means of long slender creeping stems. Dicksonia lanata, too, another small treefern, but with a stout trunk, is frequently plentiful in some places, and may then form much of the undergrowth.
The kahikatea forest consists almost exclusively of Podocarpus dacrydioides— multitudes of long, straight trunks, like masts of ships, rising from the swampy ground. High up some of the stems climb the New Zealand screw-pine, the kiekie (Freycinetia Banhsii), which also everywhere forms a rigid entanglement along the forest floor. Dead trees bridge the ever-present pools of water, and certain shrubs, of which in the north Coprosma tenuicaulis is one, form more or less dense thickets.
* This is specially true of the northern forests. Those of the Thames and the Waitakerei Range contained much more tawa (Beilschmiedia tawa).
Variation and Distribution of the Mixed Forest.
The mixed forest varies according to latitude and altitude, but a general groundwork of plants is always present. Many northern forms are wanting in the south, and, conversely, the more important southern species are less frequent in the north at a similar elevation. Latitude 38° forms a fairly definite boundary for quite a number of trees and shrubs, and latitude 42° a second boundary, though, the former, and to a greater extent the latter, is overstepped in several instances.
The pines (species of Podocarpus and Dacrydium), as they are popularly called, but more correctly designated taxads, since they are related to the yew (Taxus), are everywhere important members of the society under discussion. Confined to the north are—the taraire (Beilschmiedia tarairi), the mangaeo (Litsea calicaris), the makamaka (Ackama rosaefolia), the tawhero (Weinmannia sylvicola), the toatoa (Phyllocladus glaucus), and, some other trees and shrubs.
Amongst the trees not spreading much beyond latitude 42° are some very common ones of the northern forests. Some of these are—the karaka (Corynocarpus laevigata), which reaches Banks Peninsula; the tawa (Beilschmiedia tawa); the kohekohe, or New Zealand cedar page 47(Dysoxylum spectabile); the rewarewa (Knightia excelsa); the pukatea (Laurelia novae-zelandiae); the tanekaha (Phyllocladus trichomanoides); and some of the New Zealand olives.
The southern mixed taxad forest extending from latitude 42° to the south of Stewart Island is distinguished rather by the absence of the northern plants than by any peculiar species of its own, though such are not lacking. The Town Belt of Dunedin consists of a remnant of such a forest, and small pieces still exist all over the east of the South Island. But in the west and south the ground is still occupied by mighty forests, which for luxuriance of growth, wealth of ferns, lianes, mosses, and liverworts can hardly be surpassed. Here, too, many plants found in the North Island only in the subalpine region occur at sea-level.
The Beech Forests.
* Sometimes a species of Rubus is present (R. schmidelioides, var. coloratus).