Plates XXXIX. and XL.
This fine genus is endemic in the Antarctic islands, and com prises three species, two of which were discovered during the visit of the Antarctic Expedition under Sir James Ross in 1840, and were described by Sir Joseph Hooker, the botanist to the expedition, in the first volume of his grand work on the flora of the Antarctic islands, published in 1845. The occurrence of such striking and beautiful plants on those small islands could not have been anticipated, and their discovery excited considerable interest in the botanical world; but it was scarcely to be expected that half a century would elapse before further information respecting them would be available.
Fine plates were given by Hooker of the two species described by him; but by some mishap a leaf of P. speciosum appears to have been drawn by the artist as the leaf of P. criniferum, and has caused some confusion. In the botanical portion of D'Urville's “Voyage au Pole Sud” M. Hombron gave a fine plate of P. criniferum under the name of Albinea oresigenesa, which was published in 1845; but, owing to his death before the letterpress was issued, the plant was described by M. Decaisne asPleurophyllum hombroni.
In the “Transactions of the New Zealand Institute”* Mr. J. Buchanan, F.L.S., has described a third species under the name of P. hookeri. The description is accompanied by a plate which was unfortunately drawn from a specimen of P. criniferum, and does not represent the plant described in the text. When botanizing in the Auckland Islands I collected a plant which evidently differed from both the species described by Hooker, as well as from Buchanan's drawing of P. hookri. I therefore came to the conclusion that it was new, and distributed specimens under the provisional name of P. gilliesianum; but a careful study of Mr. Buchanan's description of P hookeri shows that it is certainly the plant which he intended to describe under that name. For this reason I retain the name given by him, notwithstanding the discrepancy shown in his drawing.
It is therefore desirable on various grounds that the recently-acquired knowledge of this interesting genus should be placed at the disposal of botanists. I have embodied it accordingly in the revised descriptions which follow.
It may, however, be worth while to point out that Pleuro-phyllum, like Olearia and Celmisia, differs from Aster chiefly in habit, and that much can be said in support of their union, as proposed by Sir Ferdinand von Mueller with regard to Olearia and Celmisia. Should this step be adopted Chilio-trichium and other genera must be included, and the large genus Aster would become unwieldy, as long since shown by Bentham.Pleurophyllum is therefore maintained in its present position chiefly on grounds of expediency.
All the species are characterized by large fleshy roots, radical leaves, and erect scapigerous racemose inflorescence. The leaves are marked by parallel nerves running from the base of the petiolar portion of the leaf. and which may either be straight or may follow the outline of the leaf. The involucral leaves are in two or three series, the disc-florets are perfect, with a 4–5-toothed limb, and the outer florets are female, usually with ligulate corollas. The receptacles are flat and alveolate, and the pappus-hairs are arranged in 2 or 3 series,
[Footnote] * Vol. xvi., p. 395, pl. xxxvii.
unequal. The scapes and peduncles are clothed with white tomentum. Sir Joseph Hooker arranged the species in two divisions:—
Radiatum.—Ray-florets with elongated corollas, 3-toothed at the apex. Principal nerves of the leaf straight, stout.Pleurophyllum verum.
Discoideum. Ray-florets with abbreviated corollas, bifid, trifid, or tripartite. Principal nerves following the outline of the leaf, slender.Pachythrix.