Art. XLVII.—On Pleurophyllum; Hook. f.
[Read before the Wellington Philosophical Society, 13th February, 1891.]
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.
1. Pleurophyllum speciosum, Hook, f., Fl. Antarct., i., 31, tt. 22 and 23.
Leaves all radical, 6in.—18in. long, 5in.—10in. broad, ap-pressed to the ground, forming a huge rosette, broadly ovate, or obovate, or unequally rhomboid, rounded at the apex or shortly acuminate, thick when fresh, strongly ribbed, ribs straight and extending the entire length of the leaf, loosely tomentose below, villous or setose above, the bristles being intermixed with moniliform hairs. Racemes erect, with numerous linear leafy bracts. Heads 1½in.—2 ½in. in diameter; disc florets purple; rays purple or whitish. Achenes strigose.
Hab. Auckland and Campbell Islands. Sea - level to 800ft.
A magnificent plant, of which there are two trivial forms: a, with leaves closely appressed to the ground, and with but few beaded hairs or none, ray-florets whitish or purplish-white; and b, with sub-erect narrower leaves, abundantly clothed with moniliform hairs; ray-florets of a deep violet-purpled The first is the prevailing plant on the Auckland Islands, the second on Campbell Island. In some specimens a few distant prickle-like points or teeth may be found on the margin of the leaves by close search.
The remarkably stout parallel ribs, from 15 to 30 in number, give the leaf a plicate appearance; as if it had been folded longitudinally, which is well seen on making a transverse section across the middle, and is not found in any other species. The inflorescence may be spiciform with very short peduncles, or lax and open with elongated peduncles which are sometimes 6in. in length; the bracts are more or less villous or tomentose below, with a few scattered hairs above, sometimes indeed with a few jointed hairs. Heads from 8 or 10 to 20 or more; involucral leaves linear-acuminate, clothed with scanty hairs or almost tomentose. Ray-florets female, arranged in two or three series, tubular below. Achene strigose; pappus-hairs in three series, not thickened upwards.
2. P. criniferum, Hook, f., Fl. Antarct., i., 32, tt. 24 and 25.
Radical leaves, 1ft.—4ft. long, 4in.—12in. broad, with long sheathing-petioles, sub-erect, spreading (except the leaf), oblong-lanceolate, ovate-lanceolate, or almost ovate, usually acute, membranous but firm, white with, thin tomentum beneath, upper surface slightly scabrid or setose, margins with a few distant projecting teeth. Stems 2ft.—6ft. high, stout, strongly grooved, cauline leaves sessile, white above and beneath. Heads discoid, 1in.—1½in. diameter. Involucral leaves ovate-acuminate, or oblong, sparingly ciliate. Ray-florets short, bifid or trifid or tripartite. Achene strigose; pappus - hairs slightly thickened upwards. Pleurophyllum hombroni, Decaisne, Bot., Voy. an Pole Sud, p. 36. Albinea origenesa, Homb., Icon., t. 4, Dicot. Phan. P. hookeri, J. Buch., Trans. N.Z. Inst., pl. xxxvii.
Hab. Antipodes Island, T. Kirk. Auckland and Campbell Islands, Hook. f. Macquarie Island (?), Professor Scott. Sea-level to 1,100ft.
The petiolate leaves at once distinguish this species, which is easily recognized even at a considerable distance. The leaves vary in outline to even a greater extent than stated in the descriptions, some specimens being almost linear-lanceolate, others obovate-lanceolate, and others again almost orbicular-ovate; the sheathing-petioles sometimes equal the lamina, at others they are not one-third of its length, but they, are never absent, and are invariably tomentose below: the cauline leaves should be considered as large bracts; they are never petioled, and are usually tomentose on both surfaces; they give the entire plant a handsome conical form, which is very distinctive. The curious projecting marginal teeth are sometimes reduced to mere points, but are rarely absent; the principal nerves, 7 to 15, are extremely slender, and follow the outline of the leaf; they may easily be traced from the base of the petiole. Flower-heads from 15 to 30 or more, the terminal being the largest; peduncles varying in length from 1in. to 6in., erect. The rays are few and very short, so that the discoid form of the anthodium is not impaired. The pappus-hairs are in three series, and slightly thickened above, as observed by M. Decaisne.
The examination of numerous specimens in the living state demonstrated the impossibility of maintaining P. hombroni as a species distinct from P. criniferum. The supposed absence of the petiole in P. criniferum is clearly due to the error in the original plate; the other characters to which M. Decaisne attaches importance are the longer peduncles, the widely separated stigmas, and the slightly clavate hairs of the
pappus. The divergent condition of the stigmas is the only point that could prove of the slightest value for specific purposes, and that is doubtless due to the more advanced period of the flowering-season at which the specimens collected by MM. Hombron and Jacquinot were collected. My specimens collected in January have most of the styles in a divergent condition, and but few approximate; but the English Antarctic Expedition finally left these islands on the 17th December, which was a very early period for these southern plants, and enhances the feeling of admiration with which the large amount of work accomplished by the distinguished botanists who accompanied the expedition is necessarily regarded.
Professor Scott includes P. criniferum in his catalogue* of the plants of Macquarie Island; but his specimen must be referred to the next species. It is extremely probable that both species occur there.
3. P. hookerianum, J. Buchanan, in Trans. N.Z. Inst., vol. xvi. (1883), p. 395, in part, excl. pl. xxxvii. P. gilliesianum, T. Kirk, MS.
Radical leaves 6in.—10in. long, 3in.—4in. broad, white on both surfaces with silky, lax, or close tomentum, flat, appressed to the ground, forming a rosette; obovate or oblong obovate, abruptly acuminate, narrowed into a broad sheathing membranous base; principal ribs 9–13, with numerous intermediate parallel nerves, marginal teeth reduced to small points. Scapes 1–3, 15in.—24in. high, naked below, except 3 or 4 lanceolate bracts at the base. Heads hemispherical or almost globose, ¾in. diameter. Involucral leaves linear, acute or acuminate, the outer with a few scattered hairs. Ray florets few or 0, ligulate corollas short, bifid or bilobate. Achene silky, pappus hairs in three series, not thickened upwards.
Hab. Mountains above Carnley Harbour, Auckland Islands, T. Kirk; Campbell Island, J. Buchanan, T. Kirk; Macquarie Island, Professor Scott ! 600ft.-1,200ft.
Easily distinguished by its silky acuminate leaves, rayless, hemispherical, or globose heads, and its small size. The middle nerves are sometimes so close as to form a kind of false midrib in the middle third of the leaf, but widen out in the narrow basal portion. The scape is rigid, and carries from 15 to 24, heads on spreading peduncles, varying from ¼in. to 1in. in length, with a linear almost filiform deciduous bractlet at the base of each; in some, specimens the upper portion of the scape is so deeply grooved that it becomes angular. In most respects the ray-florets resemble those of P. criniferum,
[Footnote] * Trans. N.Z. Inst., vol. xiv., p. 382.
except that they are smaller, and are rather bilobate, or even emarginate, than deeply bifid; they are also of a deep lurid red or reddish-purple.
As pointed out by Mr. Buchanan, there can be no doubt that this is the supposed dwarf mountain form of P. criniferum mentioned in “Flora Antarctica,” p. 33, “with all the leaves lanceolate and more densely silky, more nearly approaching Argyroxiphium than the ordinary state.” The early period of the flowering-season at which the expedition visited the islands doubtless accounts for the characters of this species not having been recognized, as it is very late in developing its flowers, which could scarcely be fully expanded before Christmas.
Description of Plates XXXIX. and XL.
Pleurophyllum hookerianum. Leaves, three - fourths of the natural size.
P. hookerianum. Scape, two-thirds the natural size. 1 and 2, Ray-florets. 3. Disc-floret (enlarged).