Art. XXXII.—A few Observations on the Tree-Ferns of New Zealand; with particular Reference to their peculiar Epiphytes, their Habit, and their manner of Growth.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 19, 1886, Page 252

Art. XXXII.—A few Observations on the Tree-Ferns of New Zealand; with particular Reference to their peculiar Epiphytes, their Habit, and their manner of Growth. By W. Colenso, F.R.S., F.L.S., etc. [Read before the Hawke's Bay Philosophical Institute, 9th August, 1886.] Plate XIX. I.—General, or Common. Not being acquainted with the living botany of the South Island, my remarks will be necessarily confined to the tree-ferns of the North Island: at the same time I think that many of those plants are nearly as common there as they are here. Tree-ferns are general throughout the North Island, in forests, on the edges of woods, and on the banks of streams; they are found in dry hilly woods as well as in the low wet ones, but are more numerous and gregarious in the latter. Mostly growing singly, scattered among the trees of the forest; not unfrequently, however, in small clumps, especially on low alluvial flats or tongues of land in the woods bounded on two sides by watercourses; and, more rarely, in tolerably large and continuous groves in wet situations between hills, in forests. The number of species at present known of tree-ferns is 11.* Of these, 7 are described in the “Handbook, Flora of New Zealand,” and “Synopsis Filicum;” and 4 (since discovered) in “Trans. N.Z. Inst.,” vols. xi., xv., and xviii. These are classed under 4 genera, viz., Cyathea, Hemitelia, Dicksonia, and Alsophila. Of those 4 genera, Cyathea has 5, and Dicksonia 4, species; Hemitelia possesses 2, and Alsophila

but 1. This last fern is much more rare, and affects a higher altitude than the others, having been only met with by me in the Fagus forests of the Ruahine mountain range, 2,000 feet altitude and upwards. Of all the genera, Dicksonia is the most common, especially in the southern parts of this island. Most of the species are endemic; one or two of them are stated to inhabit Tasmania and Australia; and the most striking and distinct one of all, Cyathea dealbata (the “Silver-tree-fern”), is said to be found in Lord Howe Islands, in latitude 32° S., between the North Cape of New Zealand and Sydney. They are usually of a single stem, erect and columnar, and devoid of branches, with a spreading crown of large regular and elegant palm-like fronds, gracefully radiating from the top and forming a living circle. In some species, especially of Cyathea, (e.g., C. medullaris, Forst., and C. polyneuron, Col.), their fronds attain to a very large size; I have measured them 15–20 feet long and proportionately broad; when large they are gracefully arched; when small are often extended, and nearly plane. Sometimes, however, their stems are inclined, others are gradually curved, and others drooping—particularly when springing from the sides of a declivity or ravine, or when over-hanging a stream. They are of various heights and thicknesses, some species being taller and slenderer than others, ranging in height from 6 to 45 feet, and in thickness from 4 inches to 2 feet: only one species, however, (Dicksonia fibrosa, Col.), attains to the maximum thickness, while Dicksonia squarrosa, D. gracilis, and most of the species of Cyathea and of Hemitelia are among the tallest. Our single known species of Alsophila is the shortest, and is sometimes stemless. They are very rarely met with bearing branches; I have, however, seen a few 2-branched, and two specimens 3-branched; and occasionally 2, 3, or 4 springing closely together from the ground, as if fascicled below at the base. Sometimes their trunks are quite clean, and devoid of epiphytal vegetation; more commonly, however, they are clothed with a dense mass of epiphytes; the stems of some species, when clear, often present a neat appearance throughout, from the regularity of the broken bases of their stipites, which add much to their beauty; while others show no such remains, but, instead, a dense and everincreasing mass of hardened surface rootlets, which generally assume a pretty even appearance, growing circularly around the stem after the manner of bark, but now and then shooting downwards irregularly in long shaggy masses; this last feature, however, generally pertains to the lower side of curved stems. And while on some trunks there are few or no withered fronds hanging from above beneath the living crown of the fern-tree, others are completely enveloped in their old pendulous fronds,

the growth of many years, presenting a curious bushy spectacle, appearing in the quiet sheltered recesses of the ancient forests as if no disturbance had ever there taken place, for not one old frond had fallen from above! As a natural consequence, in such cases the stems underneath are clean and free from epiphytes. The epiphytal vegetation common to the stems of the tree-ferns is in some respects peculiar and worthy of notice. For, while such is mainly composed of some of our smallest and most delicate ferns, (of Hepaticæ, and one or two species of mosses, and not unfrequently a small Astelia), some of the larger trees of the forest are often seen springing from their stems; these not unfrequently flourish in their peculiar situations, and sometimes grow to a large size, lofty, overtopping the fern-tree itself, and sometimes, though rarely, killing it by its close embrace; more usually, both seem to flourish and enjoy their curious reciprocal attachment. The trees that are commonly found so combined with the fern-tree are Weinmannia (sps.), and Panax arborea, and Ackama rosæfolia in the forests at the North, the peculiar locality of this genus. The ferns that often clothe and completely hide the trunks of the tree-ferns comprise the smaller species of Hymenophyllum, as H. nitens, H. tunbridgense (and its varieties), and H. rarum; also, Trichomanes venosum, and its near ally T. venustula; indeed, such may truly be called the proper home of these two Trichomanes, as well as of Hymenophyllum tunbridgense, for nowhere else are these pretty little ferns to be found growing so luxuriantly. It is a beautiful object to contemplate the whole stem of a large tree-fern so dressed and decorated by Nature! often extending completely and closely around the trunk, and that for several feet; their little elegant glistening light-green fronds, so very regular, too, in their manner of pendulous growth, overlapping each other and imbricating like scales. Here is also the home of that highly curious fern Tmesipteris, never found growing on the earth, and rarely found on any other plant; and very recently a small and new species* A full description of this little novelty has been prepared, and will be iven in a following paper. of the closely-allied genus Lycopodium has been detected growing thereon; while a small elegant moss, Hymenodon piliferus, (the only New Zealand species of that genus), is sure to be found deeply ensconced between the numerous dead stipites, and growing freely in its dry abode. Two or three species of delicate small frondose Hepaticæ (e.g., Symphyogyna sub-simplex, S. brevicaulis, S. simplex, Podomitrium, Phyllanthus, etc.), are also at home there, snugly nestling deep in the crevices of the stems, from which it is a difficult matter to dislodge them without breaking; while some of the larger Hepaticæ, as the dendroid Plagiochilæ, areoften found growing

luxuriantly upon their trunks, completely enwrapping them below, especially in low, wet, shaded woods. Other and larger ferns than those mentioned are not unfrequently to be met with, depending from the trunks of the tree-ferns, as Hymenophyllum dilatatum, H. demissum, H. multifidum, Asplenium falcatum, A. flaccidum, and Polypodium (species); also Lycopodium varium; but then these are much more common and plentiful elsewhere, both on trees and on the ground. II.—Particular, or Uncommon. Under this heading I wish to state what I have more recently seen, which, indeed, is the main cause of my writing this paper. During the last three to four years I have noticed some extraordinary things pertaining to the tree-ferns. 1. As to their great number in one spot, and their manner of growth there.—In certain unfrequented localities in the dense forest of the Seventy-mile Bush, which I explored at different times, I suddenly came upon two or three groves of tree-ferns: one in particular I will attempt to describe. On a flat in the heart of the forest, in a deep hollow lying between steep hills, the bottom of which for want of drainage was very wet and uneven, and contained much deep vegetable mud and water even in the driest summer season, I found a large and continuous grove or thicket of very tall tree-ferns, chiefly Dicksonia squarrosa, and D. fibrosa, with a few of Cyathea dealbata intermixed, with but few forest trees and shrubs growing scattered among them. I suppose they occupied about 3 roods of ground, and I estimated their number to be from 800 to 1,000. They were all lofty, from 25 to 35 feet high, and in many places growing so close together that it was impossible to force one's way through them. Their trunks were most profusely covered with the usual epiphytal ferns (those smaller ones already mentioned). Conspicuous, however, among them, was that very rare fern in these parts, Hymenophyllum subtilissimum, Kunze, (H. frankliniarum, Col.,* Hymenophyllum æruginosum, Carm., of “Handbook N.Z. Flora.”) which literally clothed their trunks from top to base, intermixing below in the more humid spots with a fine dendroid Plagiochila (sp. nov.) of most luxuriant growth. † The description of this fine species will be given in a following paper. The ground, too, with rotting logs and stumps below, was densely covered with various fine Hepaticæ of several genera, (as Plagiochila, Gottschea, Lepidozia, Mastigobryum, Podomitrium, Symphyogyna, etc.), while here and there among them were several lovely and rare mosses of the genera Hypopterygium, Cyatrophorum, and Hookeria; and on the higher and drier stumps and mounds grew graceful undisturbed cushions of Leucobryum candidum, plentifully in fruit, rather a rare occurrence.

A few of those tree-ferns were 2-branched; one, I noticed bearing three branches; all of the branches were at some height from the ground, and rose just as high as the parent stock. Several of those tree-ferns grew in little clumps of 3, 4, or 5, arising from small mounds 2 feet high or so, with deep watery muddy holes between them; their stems were very close together, and appeared as if fascicled or springing from one root-stock below; while above they not unfrequently diverged from the perpendicular. Familiar as I have long been with our New Zealand forests and their denizens, I gazed with astonishment in this deep and secluded grove of tree-ferns! for I had never before witnessed such a grand display of them; neither had I seen for upwards of 40 years* Originally discovered in the mountainous woods of the interior, N.W. of Lake Waikare, in 1841, and published in 1842 in the “Tasmanian Journal of Natural Science,” vol. i., p. 378; also vol. ii., p. 183. this pretty species of soft silky Hymenophyllum that was here so exceedingly common. Very certain I am that it does not grow in those several and many scattered parts of that same extensive forest which I have so frequently visited during these last 10–12 years. From this wet wood I brought away several fine Hepaticæ; particularly that superb Gottschea, G. dichotoma, Col.,† See “Trans. N.Z. Inst.,” vol. xviii., p. 284. the largest known New Zealand species. This fine plant (which I have only detected in this locality), completely and thickly covered a large old stump, hanging gracefully down around its top, reminding one of a rich-looking fringed circular cushion or hassock. The ground or mud in many places was thickly covered with long irregular patches of an erect species of Symphyogyna, which I believe to be new.‡ Since ascertained to be such: a description of this plant will also be given in a paper to follow. This genus is mostly gregarious in small lots, but I never before saw it growing in such profusion, and so very compact and large, somewhat resembling beds of curled cress or parsley. Places and spots of botanical beauty or-novelty, however, (like all other things), have their drawbacks or opposites: the worst feature here was the very bad footing, causing much tumbling about and splashing and sinking, between slippery and hidden rotting roots and branches, into deep black vegetable mud up to one's knees; and then there was the haunting fear of some accident happening, through which I should not be able to get out of this tangled labyrinth; and, as a matter of course, in that distant and unfrequented spot, should not be easily or early found, if ever found at all! 2. As to the very peculiar growth of some tree-ferns, caused by

Sketch (Unfinished) of a Fern Tree (Cyathea Dealbata.) Encircled in Growth by A Panax Arboreum.

their own epiphytes.—Some novel instances of this nature I have occasionally met with, a few of them being very strange. (1.) I have already said tree-ferns are often found with young plants of Weinmannia (sps.), and of Panax arborea, springing from their stocks at some distance above the ground. These trees also grow to a considerable size—of 3, 5 and 7 feet, and are well-branched and flourishing, although their rootsdo not reach down to the earth. A few of them, however, of a much larger size, 14–16 feet high, that I have seen and examined, send down their trunks (I can hardly term them roots) from the place where they had sprung from seed on the stock of the fern-tree into the ground, (sometimes in two or three branches or ramifications), closely adhering to the fern-tree and partly intertwining its stem. (2.) In a dry wood on the bank of the River Mangatawhainui I saw several specimens of this nature. One aged fern-tree had its base completely surrounded at the surface of the ground by a large Weinmannia racemosa, that had originally sprung from its stock, which also adhered to it above on one side for several feet. Another fern-tree had a Weinmannia embracing it on the one side, and on the opposite side a Panax arborea, (this latter very largely and closely), and both trees had originally sprung from the trunk of the fern-tree, and thence descended to the earth. I noticed one tree-fern in particular, that was wholly separated below from the earth, having its caudex closely hugged for 2–3 feet by a large branching Panax arborea, whose branches or divided stem (I cannot call them roots) descended from the original point of first growth above in the stock of the fern-tree, and enwrapping it at intervals had held it fast, wholly immovable, as if the two trees had coalesced into one. This was on the side of a dry hill, and the rains, etc., in past years, had completely washed away the soil and small vegetation from beneath and around the base of the fern-tree; the fern, however (a Cyathea dealbata), was of a large size and most luxuriant growth. I had detected two or three instances of that nature before, but those fern-trees were only partially severed from the earth at their bases, while this one was wholly separate, and from its appearance had been so for many years, as no fresh rootlets were emitted there. (3.) Strange, however, as that instance may appear, I have still a more curious anomaly to mention, which, as far as I know, is quite unique. Four years ago, while botanising in the high and dry woods near Matamau, I came upon a fine tree-fern (Cyathea dealbata), whose caudex below was almost wholly surrounded by its former epiphytal foster-child—a stout spreading specimen of Panax arborea, from which, or out of which! the fern-tree luxuriously grew, as if it were springing from a large vase! On the one side (or, rather, speaking correctly, on three

sides), the fern-tree was wholly enclosed; and this was all the more plainly to be seen, from the fact of the trunk of the Panax being bare of epiphytal vegetation, so that its light-coloured and clean bark showed in strong relief against that of the darker fern-tree in the few narrow interstices on the one side where it still slightly appeared. Another great curiosity was the entire unbroken appearance of the Panax on the one side of the fern-tree, which was completely covered by it; there was no trace discernible of any cicatrices or joinings in its bark, which was even. The tree, or pair so strangely conjoined, stood in a small glade or open space among the trees of the forest that were densely thick around, which circumstance, together with the dark-green foliage of the very large leaves and sprays of the Panax, above and around the delicate pure white fronds of the fern (viewed from beneath them and looking up), with the blue sky here and there in the background seen through their branches, caused the two trees to be seen to a great advantage. The tout ensemble was both unusual and charming, and served to bring to mind portions of Ovid's metamorphoses of trees. Another pleasing thought arose from the consideration of this tree (Panax), in its so clasping and sending out and down its root-like branches, (which it never does when growing in the earth in its native woods), thus showing its real natural affinity in latent habit to those other genera of that same natural order in which it is placed, (e.g., Hedera, Gunnera, etc.), which so largely and constantly grow and adhere by their climbing root-lets; and yet the ivy (Hedera helix) sometimes grows as a standard. I visited that spot on several occasions during two years, and always with feelings of admiration; and was so much surprised and pleased with my “find,” that on two of those visits, having taken my portfolio with me, I attempted to take a drawing of it; (in one of those times, however, being caught in heavy rain!) but, owing to the loss of drawing and writing power in my thumb, I made a poor job of it. Still, such as it is, and unfinished, I bring it before you, as by it you may be the better able to know somewhat of the relative sizes and appearances of the two curiously-entwined and coalesced plants. I took accurate measurements of this botanical phenomenon, and the following is the result:— 1. Height of caudex of Cyathea from the ground to the springing of its living fronds, 7ft. 6in. 2. Height of Panax, about 18ft. 3. Girth of both, taken together at base, 6ft. 4. At 5ft. 3in. from the ground the Panax tree forked into two stout, erect main branches. 5. Girth of both plants under the forking of the Panax, 5ft. 3in.

6. Girth of main branch of Panax, 2ft. 10in.; of the other, 2ft. 3in. 7. Girth of Cyathea, immediately under its crown of fronds, 5ft. 8. Breadth of the narrow interstices of the stem of the fern-tree not yet covered by the Panax: at the base, 2in.; above, in the widest part, 3in. 9. The fronds of the fern extended about 9ft. each way, forming a flattish arch. 10. The lower horizontal branches of the Panax extended nearly equal with the fronds of the fern. 11. The trunk of the Panax below was quite bare of epiphytal vegetation (only a small young creeping plant of Metrosideros scandens just climbing up at one corner), but large fronds of Polypodium billardieri and other ferns hung pendulous from between the two upright limbs of the Panax and the Cyathea. 12. The longitudinal edges of the root-like descending lower limbs of the Panax showed exactly the appearance of the back of a healthy tree from which a limb has been clean cut off, growing-in with thick round advancing margins over the wound.