Our visit to Arid Island was not made under favourable conditions for the investigation of its botany; most of the vegetation of the open land having been burnt off by a party of Maories, a few days before we landed;
and our stay being limited to a few hours by the unsettled state of the weather.
Although it was impossible to make even an approximate list of the plants of the island, sufficient was observed to show, it possessed a flora which comprised a greater number of forms than could be collected on the islets off the west coast of the Great Barrier; and that the general character of its flora approximated closely to that of the Little Barrier Island, which it so nearly resembles geologically. A complete examination of Arid Island and the Little Barrier, would probably result in the discovery of other plants common to both, but absent from the Great Barrier, besides those observed by us.
The flora of the island may be roughly divided into, Ericetal,—or plants of the open land;—Sylvestral,—or forest plants;—Littoral,—or beach plants; and Uliginal,—or marsh and swamp plants. It need scarcely be remarked, that these terms are not always capable of precise application.
The greater portion of the central area of the crater, and its rim, is occupied by Ericetal plants; in the lower parts, a dense growth of Pteris esculenta, which often attains the height of six feet, intermixed with occasional tufts of Phormium tenax, renders all progress slow and laborious. On higher parts and in open places, the fern is supplanted by Leptospermum scoparium and Pomaderris phylicifolia, sparingly intermixed with bushes of Coprosma robusta, C. lucida, Carmichœlia australis, Leucopogon fasciculatus, Veronica salicifolia, Coriaria ruscifolia, and other small shrubs. Agrostis œmula, Leucopogon Frazeri, Drosera auriculata, Lobelia anceps, Haloragis micrantha, Lagenophora Forsteri, etc., etc., were common amongst open fern, together with the ubiquitous introduced plants, Erigeron canadensis. The pretty Ophioglossum lusitanicum was seen on tufaceous ledges, and was afterwards observed, in exactly similar habitats, on the Little Barrier, but appeared to be entirely absent from the Great Barrier. Many specimens had two or more scapes springing from same root, a peculiarity it shares with other forms of the genus in New Zealand, although all the forms collected in the northern hemisphere have invariably solitary scapes. On the highest points of the island, as, in fact, of all islands and headlands in the North of New Zealand, Astelia Banksii and Metrosideros tomentosa were invariably found. Astelia Banksii, we may remark, is always rupestral in its habitat, never epiphytal,—nor is it found at any great distance from the sea, so far as our experience extends. From personal observation, we can testify, it is abundant on rocks at Mercury Bay, where we sought for it in vain “on the limbs of trees,” as reported in the Handbook of the N. Z. Flora. Astelia Cunninghamii, is both epiphytic and rupestral, and is most frequently found inland.
The sheltered open spaces at the base of the cliffs on the exterior of the crater, and large portions of the northern and southern sides of the interior, are occupied by the Sylvestral portion of the flora in the crater itself, forming a somewhat open bush, although few of the trees attain large dimensions. As might be expected, the Pohutukawa (Metrosideros tomentosa), is abundant, although greatly inferior in size and appearance to the fine specimens of this tree on the Great Barrier, and which are probably unsurpassed. In the crater, this tree resembles M. robusta, in its free and erect habit of growth, but on the cliffs it presents the dis-
torted appearance so commonly seen about Auckland. The principal trees of large size are the Rimu (Dacrydium cupressinum), and the Tarairi (Nesodaphne Tarairi). Amongst smaller trees and shrubs are Dysoxylum spectabile, Melicytus ramiflorus, Corynocarpus lœvigatus, Dodonœa viscosa, Coprosma grandifolia, Panax Lessonii, P. arborea, Shefflera digitata, Corokia buddleoides, Olearia Cunninghamii, Brachyglottis repanda, Geniostoma ligustrifolia, and many others, but perhaps the most remarkable is Pisonia umbellifera a few trees of which were found growing amongst young and large-leaved specimens of Corynocarpus lœvigatus, which it closely resembles in the shape and colour of its leaves; and in the absence of its flowers and fruit, presented an anomalous appearance,—“like, yet unlike.” Some of its leaves measured fully eighteen inches in length, and seven inches in breadth. It was subsequently collected, in a curiously similar habitat, on the Little Barrier Island, but was not found on the Great Barrier.
The Littoral and Uliginal plants present nothing worthy of special notice, nor indeed had we sufficient time to examine them closely, Samolus repens, Salicornia indica, Selliera radicans, and others of rupestral habitat, are abundant at the base of the cliffs. Amongst the Arenarian plants are Coprosma acerosa, Convolvulus Soldanella, and Spinifex hirsutus, the last named curious grass formed large tufts, with prostrate culms, sometimes thirty feet or more in length, which throw out roots at the joints, and aid in binding the shifting sands. The cultivated radish, Raphanus sativus, is also found growing with the above on the sands at the head of the little harbour.
The Raupo, Typha latifolia, var. angustifolia, and other uliginal plants, find a suitable habitat, although of limited extent, near the centre of the island.
The notes just read must be considered as merely a contribution to the botany of Arid Island. We venture to express the hope that some member of the Institute may visit the island under more favourable circumstances, than fell to our lot, and be able, at least, to make a complete catalogue of its phœnogamic plants and ferns; not only on account of the interesting nature of the locality; but because of the positive value possessed by an exact and minute knowledge of the local distribution of plants, as an element in the ultimate circumscription of their specific limits.