NATURE NOTES

Evening Post, Volume CXII, Issue 3, 3 July 1926, Page 15

NATURE NOTES

- NEW ZEALAND FERNS

A WEALTH OF SPECIES

(By R. H. D. Stidolph, R.A.0.U.)

New Zealand has been justly called the "Land of Terns," for there are few countries of its size that can claim such a wealth of species and such abundance. Even the most unsympathetic visitor to the bush cannot but admire the luxuriance, the diversified forms and tho outstanding beauty of these forms of plant-life. Ferns form tho most highly organised division of the flowerless plants, which are characterised in the main by being built solely of cells. The furry red-brown patches on the back of the fern leaves —which some people think is a disease —consist of thousands of minute capsules, each containing about 64 microscopic spores. Under suitable conditions, each spore develops, not into a fern like'that by which it was produc- . ed, but into a tiny heart-shaped green scale, which bears on its under surface two kinds of sexual organs—the counterpart of the anthers and ovaries of flowering parts. The male organs contain motile bodies, which find their way to the female organs and fertilise them. The result is the production of an embryo from which in due course arises a leafy fern-plant like that which produced the spore. Ferns are found in a great variety of situations. Although the forest constitutes the home of the majority, there are some that thrive on dry rocky localities—others that cannot exist away from the sea-spray, others that delight in damp pastures, and does not one—the bracken—even offend by being one of the worst noxious weeds in the country f Even in ths woods, there are those that carpet the forest floor, there are the magnificent tree ferns capped with their crowning glory, there are climbing • ferns that clothe the trunks of the forest giants, and there are others perched as epiphytes in some crevice or hollow high up overhead. * • • There are about 140 species of ferns to be found in New Zealand. The tree ferns occupy premier position, and the black tree fern or mamaku is the queen of all. It is tho largest of our tree ferns, often attaining a height of 60 feet and occasionally more, and can be at once distinguished by the caudex or trunk being covered with flattened or slightly hollowed scars, where the bases of old fronds have broken off. This magnificent species is abundant except in the east of Canterbury, Otago, and Stewart Island, and also occurs in south-east Australia, Tasmania, and several of the Pacific Islands. Probably the most generally distributed of New. Zealaud tree ferns is the ponga or silver tree fern, usually to be identified at once by tho milk-white under-surface of the fronds. The weki or wheki is another abundant species, easily recognised by the slender blackish trunk, harsh and coriaceous fronds, or by the numerous black bases of old stipites, about nine inches long, which remain all over the caudex and stand nearly straight up against it. An allied species, the weki-ponga, with a caudex extremely stout in appearance, owing to the mass of matted fibrous aerial roots which envelopes the actual caudex, is one of the moat handsome species, owing to tho great number of fronds which form the crown and the way in which they rise in tiers, one above the other. A mountain species, usually found between 2000 feet and 4000 feet altitude, although classed as a tree fern, departs from the usual method of growth and has a caudex that lies on the ground, with only tho end turned upwards. If, in travelling along the end of the caudex, it encounters a fallen log or other obstacle, it climbs over it and descends to the ground again on tho other side, to continue its course. Altogether, there are ten species of tree ferns in New Zealand, tut two of these are found only in the Kermadee Islands. •

Now Zealand is especially rich in filmy ferns, known officially as hymenophyllum, which is derived from the Greek hymen, a film, phyllon a leaf, and is one of the most beautiful of the genera of ferns, almost entirely confined to shaded localities. New Zealand can claim twenty species of these woodland gems. One of the most handsome species of the genus, H. dilatatum, which grows plentifully in the damp parts of gullies, upon tree-trunks and rotten logs, sometimes attains a length of two feet. Another species, H. Cheesemanii, forms cushions on the branches of trees, or creeps amongst moss, from which it is hardly distinguishable, being so minute, usually a quarter of an inch to one inch in length. Between these two extremes the many other species of filmy ferns vie with each other for beauty, the larger species growing pendulous on tree trunks and .others carpeting the forest floor. Seven species of Trichomanes, a genus closely allied to the preceding, are found in this country, and one —the kidney fern—is probably the best known, most distinctive, and most remarkable of all New 7 Aland's ferns.^ The dark semi-trans-parent colour, the distinct veinrng, the glossy kidney-shaped fronds that often clothe many square yards of the ground or often envelop to a great neight some forest tree trunk, mark the kidney fern as one of the most treasured possessions of tho forest.

No mention of New Zealand ferns could,bo complete without reference to the maindenhair ferns. They are known to scientists by the generic name of Adiantum, from the Greek word "adiantos" dry, so named because water will not lie on the surface of these ferns. The largest of New Zealand's six species, which reaches a height of up to three feet and sometimes more, enjoys a very restricted habitat in this country. It has only been reported from the alluvial banks of the Northern Wairoa Bivex, and from the Manawatu River and its tributaries from Woodville to below Palmerston North. The magnificent Prince of Wales' Feather Fern is another cherished possession, which thrives in dense moist forests from Te Aroha and Pirongia southwards. In the late spring this plant looks especially beautiful. The fronds of the previous year, perhaps ten or twelve in number, are beginning to droop, but still retain the semi-trans-parent dark green colour, and above these there are an equal number of young sub-erect fronds'of bright delicate green, contrasting beautifully with the old ones.