NATURE NOTES

Evening Post, Volume CX, Issue 52, 29 August 1925, Page 13

NATURE NOTES

THE POOR KNIGHTS ISLANDS

A BOTANICAL EXPEDITION

(By R, H. D. Stidolph, 8.A.0.U.)

The Poor Knights Islands near Wha»ngarei, lying some fifteen mile* from the mainland, were visited at tha end of last year by. two memben of tha stn.iV of the Dominion Museum, Mwn. W. R. B. Oliver and H. Hamilton, ton tho purpose of investigating the wild Ufa of the group. The islands are of an extremely rough nature, and the want of good landing places ensure* their being practically unmolested. Mr. Oliver, in a paper in the "New Zealand Journal of Science and Technology," states that the islands represent fragments of tho western slopes of a volcanic -cone, tho rocks appearing' to ba entirely volcanic, whitish in colour, and probably rhyolitio in character.- A certain amount of interest attaches to outlying islands for the reason that they are natural sanctuaries for many kinds of plants and animals which are unable to maintain themselves against thsmora hardy forms of life introduced into New Zealand. Tho more inaccessible the island the l«ss frequently .will it hava been visited and the less' will the vegotation_ and fauna have been altered by alien influence. At one time Maoris oc-; cupied part of the group, but ov#r a; hundred years n.50 they shifted to tho mainland, and the islands- have sine* boen uninhabited. Apart. . therefore. from the effects of the \Mnori. and tho pigs he left behind him, the flora and fauna of tho group nre in their-prim-eval state. However, the virgin, condition 0/ the vegetation and its contained fauna has been altered to some extent by several agencies. Fire has destroyed a portion of the scrub in both of the main islets, and in its place has grown up a covering of flax and other -native species with a sprinkling of introduced species. Considerable portions -at the forest on the southern islet were cleared by tho Maoris, but has now reverted, to scrub and low forest, but, undoubtedly, of a different type from' the original coveting. Possibly the Maori is responsible for the email number (51- species of land birds now inhabiting the. . group.: Pigs left on the Poor Knight by t.ho Maoris are by far the most destructive agency present, and attempts are being made to exterminate these animals. .11*. Oliver writes: "By comparing the flora and fauna of the southern islet, "whera pigs have roamed for more than, a liuprtred years, with that on the northern islet or portions of the southern islet which aro inaccessible to these animal*, the -destructive effects can to a certain extent be gauged. . The plants of the forest floor, including seedlings of tree* are well night extirpated; some specie* are abundant in the northern ißland and almost extinct on the southern. But the most serious effect of allowing pig» in a forest undoubtedly arise* from tha destruction of tree seedlings. The whole physiognomy of the forest may be altered and its power of regeneration greats ly impaired. I'lie effect of pigi on iha fauna is best eeen in tha wipinz-out at the breeding grounds of borrowing pairels, a process wnich" involves the killing of many birds: The rare Buller'e shearwater and other petrels are practically estiuct on tha southern islet, but abundant on other islets of the group. Gannets, gulls, and terns are prevented from breediiqf on the pig-infested islets.' Passing on to the plant* of the '■'""fa Mr. Oliver state* that over 120 ipaakt of ferns and flowering plants war* collected by the expedition. The moat interesting fact to be recorded i» that many of the common tree* on tha Poor Knights are species that are fast becoming extinct on the mainland, and tha islands, therefore, constitnte a national museum for such plants at the whau, parapara, tawapou, and the broad-leav-ed maire, besides some shrubs and herbs. The tawapou, known scientifically as sideroxylon costatum, is a tree that finds refuge in islands lying off tha; coast. On the mainland it is found in various localities or headlands as far South as the East Cape district. It is a large tree on the Poor Knights. Tha wood is hard and the bark when cut exudes copiously a white latex. It is the sole representative in New Zealand of a large tropical genus. The parapara is also a large tree on the Poor Knights. The leaves are large and membranous, being exceeded in size among New Zea^ land plants only by the puka, ■ Two other interesting points about the parapara aro the exceedingly soft nature of the wood, which on drying shrinks after the. manner of piths, and is at the same time readily attacked by fungi, and the very sticky fruits in which small birds may become entangled and perish through inability to free themselves. Tho whau, one of the most beautiful New Zealand trees, is abundant on the. Poor Knights. It has been also extirpated on the mainland, as cattle and sheep appear to relish it, and it is now only found in localities inaccessible to those animals. The broad-leaved maira is very scarce, only one plant—a. large tree—being noticed on tho islands.' Mr, Oliver thinks that this is in all probability due to the depredations of pigs, as young plants are plentiful in Hen Island, where there are no pigs. Tha leaves are deep glossy green with wavy ed#fls, and are very stiff and tough. The wood is very hard, but, as in'the pohui tukawa, straight-grained pieces cannot ba obtained. In addition to the localities name the broad-leaved maire is found at Whangarei Heads, Mokohinau, and Cuvier Islands.

The most notable event of the expedition was the discovery of a speciess new to science. Shortly- after landing Mr. Hamilton brought a specimen into camp from the top of tho seacliff above the tent, and later Mr. Oliver found the plant growing more abundantly. Xeronema callistemon, as this plant is callr ed, forms large tussocks, perhaps five or six feet in diameter, consisting of leaves and flowering stems three to four feet in height, and resembles a mod-erate-sized flax bush, but with stiffen iris-like leaves forming a more compact tussock than does the flax plant. The flowers are bright red in colour, and occur in heads up to one foot jn length. As in the rata the conspicuous parU of the flowers are the stamen* and pistols. "No Jew remarkable than the appearance of the plant itself," Mr. Olive* writes, "is its relationship, for the genus Xeronema was known hitherto only by tt species occurring in the mountains of New Caledonia,* The Poor Knights' a species differ in certain respects, from its New Caledonia relative, and is moreover, a larger plant. Speculation on the occurrence of these two rotated species in such distant localities is diffiV cult to avoid. A former land connection between the two points wonld be a suf. flcient explanation, and such a .connection is supported by the presence in tha two areas of other similarly related plants and animals. The kauri, karaka, puka, and the land snail Plaeoatyhwquickly come to mind, so that the discovery of Xeronema strengthens - the 1 argument for a former land connection north-eastwards from New Zealand,, a theory accepted by both biologist and geologists as necessary to explain many problems connected with the flora and fauna of New Zealand,"