Art. XXIV.—Remarks on the New Zealand Sow-thistles, with Description of a New Species.
[Read before the Wellington Philosophical Society, 21st February, 1894.]
In all probability there are no common New Zealand plants about which the ideas of local botanists and agriculturists are so confused as the sow-thistle. The range of variation in the habit and foliage of some species is so great that an ordinary
observer may be excused for doubting the specific identity of several of the forms comprehended under the same name: for instance, the plant named Sonchus asper by Fuchs exhibits in many instances rigid leaves with crisped and waved margins so closely fringed with brittle spines as to fully justify the application of the trivial name when incautiously handled. By its side may be seen another form with flat, soft, membranous leaves, more or less deeply cut into broad or narrow lobes, utterly destitute of spines. A complete series of gradations may, however, be found between the two forms, and, as their flowers and fruit present no differential characters of the slightest importance, both plants, notwithstanding their dissimilarity, must be referred to the same species.
In the “Flora Novæ-Zelandiæ,” and the “Handbook of the New Zealand Flora,” Sir Joseph Hooker recognises one species—S. oleraceus, L.—of which he considerS. asper, Fuchs, to be a variety. Bentham adopts the same view in the “Flora Australiensis.” Both the type and the variety vary to a great extent in the outline, cutting, and texture of the leaves, but may be briefly characterized as under:-
Sonchus oleraceus, L., sp. 116. Forst., Prodr. n. 282.
Leaves clasping, almost entire, or toothed, or deeply pinnatifid. Cauline leaves, with large sagittate auricles. Achenes with 3—5 longitudinal ribs, finely muricate, glabrous.
β. asper. S. asper, Fuchs, Hist. 674.
Leaves clasping, almost entire or lobed, or deeply pinnatifid, sharply toothed, sometimes rigid, with the margins crisped and spinulose. Achenes longitudinally ribbed, glabrous.
Both forms are common in cultivated land throughout the colony.
Sir Joseph Hooker considers that var. β is certainly indigenous in New Zealand, as it was collected by Banks and Solander. It is, however, certain that seeds of both forms must have been repeatedly introduced since that period, and that cross-fertilisation has taken place, since fruits of the typical form exhibit all degrees of murication—some showing only faint traces, while others are covered with small but strongly-marked pittings.
The Rev. W. Colenso, F.R.S., considers this var. β to be the puwha of the Maoris, who formerly used it for food, but abandoned it for the introduced European plant, which is less bitter. There is, however, a still more striking form which may also have been utilised by the Maoris. Although widely distributed it is somewhat local, and rarely occurs in large quantity. I do not know any European form with which it
exactly agrees. Its characters will be found in the following description:—
Sonchus oleraceus, L., γ.littoralis.
Robust, stems 1ft. to 1 ½ft. high, sparingly branched, radical leaves sessile, ovate-oblong, entire or sparingly lobed, obtuse, finely or coarsely toothed, somewhat fleshy, rosulate, and closely appressed to the ground; cauline leaves few, acute, auricles rounded or subacute. Outer involucral bracts acute, inner obtuse; achenes glabrous, 3–5-ribbed.
Hab. On maritime cliffs from Auckland to Stewart Island, but often local, and rarely occurring in great abundance.
The uniformly undivided, rosulate, slightly fleshy leaves, the more robust habit, and copious milky juice are well worthy of notice, as is the large fleshy root. I have never seen this form on cultivated land, and, as far as I am aware, it is absolutely restricted to maritime localities. The singular absence of variation is a remarkable feature when this plant is compared with the typical form and variety β
It seems not unlikely that the plant observed by Banks and Solander is identical with var. littoralis, the fruits of which resemble those of var. β, but are slightly larger. This point could doubtless be settled by an examination of the specimens in the Banksian Herbarium. It is worthy of note that Dr. Anderson, who acted as naturalist in Cook's third expedition, mentions the occurrence of “sow-thistles” in Queen Charlotte Sound: there can be but little doubt that the plant observed by him was var. littoralis.
Shortly before my old friend Mr. J. D. Enys, F.G.S., left the colony he made a hasty trip to the Chatham Islands, where he obtained specimens of a handsome sow-thistle, with leaves upwards of 2ft. in length, and large flower-heads, which he kindly sent to me, but unfortunately they were in such a bad state of decay when they came to hand that I was unable to dissect them. However, on examining the type collection of Chatham Island plants in the herbarium of the Colonial Museum I found two specimens, one of which was S. oleraceus, L.; the other proved to be identical with the plant collected by Mr. Enys. In justice to Mr. Buchanan, who arranged the type collection, it should be mentioned that both specimens are small, and in bad condition. Unhappily, my efforts to obtain good specimens so far have failed, although a valued correspondent sent me a strong root, which, however, failed to grow. It was therefore with no little pleasure I learned that the plant had flowered in the rich collection of native species cultivated by Messrs. Adams and Sons, of Christchurch, and I am indebted to these gentlemen for their kindness in sending the shrivelled receptacles and ripe fruits.
Unlike the forms mentioned in the early part of this paper, it is a strongly-marked species, as will be seen from the appended description.
Sonchus grandifolius, n. s.
A succulent herb, 2ft.-4ft. high, rhizomes stout, fleshy, creeping, sometimes 2 ½in. diameter. Radical leaves erect, 1 ½ft.—2ft. long, 4in.—7in. broad, petiole 6in.-9in. long, stout, dilated at base, but not clasping, blade oblong or ovate-oblong, deeply lobed, pinnatifid or pinnate; segments 4—6 on each side, broad, lobulate, often overlapping, coarsely doubly serrate or dentate, almost coriaceous, scabrid above. Lower cauline leaves petiolate, upper broadly sessile, not auriculate. Heads large, 1in.—1 ½in. diameter, peduncles white, with cottony wool. Involucral leaves in 3—4 series, broad, subacute, outer with a median line of spinous or almost foliaceous processes. Achenes large, broad, with 1 or 2 stout median longitudinal ribs, and about 4 finer ones, margins broad.
Hab. Chatham Islands.
The ligulate florets appear to be yellow, tinged at the apices with faint salmon-colour or purple. It is a noble addition to the New Zealand flora, and adds another remarkable species to the singular group of endemic plants on the Chatham Islands.
The fleshy rhizome may possibly prove valuable for cattle-food.