Art. LIX.—On Nephrodium decompositum,. Br., and N. glabellum, A. Cunn.
[Read before the Wellington Philosophical Society, 1st December, 1877.]
In the “Hand-book of the New Zealand Flora” these plants are considered identical; in the “Flora Novæ-Zelandiæ,” the second is described as a variety of the first. They are, however, so easily recognized at sight that a singular unanimity of opinion prevails amongst New Zealand botanists in favour of their being considered specifically distinct. I purpose, therefore, briefly to examine the differential characteristics of the two plants.
In N. decompositum the rhizome is elongated, slender, more or less clothed with chaffy scales and the distant bases of old fronds; it is frequently branched and extensively creeping so that the plant often forms patches several yards in diameter. Fronds erect, solitary, distant never tufted or
springing from the apex of the rhizome, usually from 12–24 inches in height. Stipes from half to two-thirds the length of the entire frond, clothed with scattered chaffy scales and fine pubescence, angular, channelled; the frond is from 7–10 inches wide with the apex elongated and the lowest pair of secondary pinnæ much developed, so that its general outline is pentangular acuminate; bi- or tri-pinnate, membranous, villous or pubescent; rachis slender; lowest pair of pinnæ much the largest, 5–7 inches long, 3–4 inches wide, obliquely deltoid; upper pinnules lanceolate, pinnate, or deeply pinnatifid, ultimate segments ovate or rhomboid ovate with acutely toothed lobes. Sori attached nearer the margin of the segment than the midrib.
In N. glabellum the rhizome is short, stout, densely clothed with the wiry bases of old fronds, unbranched. Fronds from 4–6 in number, tufted, springing from the apex of the rhizome and usually of less size than those of N. decompositum. Stipes always more than half the length of the entire frond, scaly at the base, naked above, reddish, channelled, from 7–10 inches long, 6–9 inches wide, deltoid, acuminate, twice or thrice pinnate, slightly coriaceous, glossy; lowest pair of pinnæ 4–5 inches long, 2–3 inches wide, less obliquely deltoid than in N. decompositum, with the basal pinnules much less developed, and rachis more prominently winged; segments pinnate or deeply pinnatifid, with the basal lobes overlapping so as to form a connected line on each side of the rachis of the lowest pinnæ; lobes obtusely toothed, veins prominent. Sori equi-distant between the margin of the segment and the midrib.
While freely admitting the close resemblance in the cutting and in the general outline of these plants, the essential differences indicated appear to me sufficient to warrant these plants being considered specifically distinct, but it is necessary to offer a few remarks on their nomenclature, which is somewhat confused, the specific name “glabellum” having been applied to both.
The earliest description of either is that of N. decomposition, by R. Brown, in his “Prodromus Floræ Novæ Hollandiæ,” p. 149 (1810). The next is that of N. glabellum, by Allan Cunningham, in Hooker's “Companion to the Botanical Magazine,” II., p. 367, and which is clearly the plant to which the name is now applied.
In the “Flora Novæ-Zelandiæ,” II., p. 39, under N. decompositum, Brown's plant is described and figured as var. a. glabellum, N. glabellum, Cunn. Although corrected by Sir W. J. Hooker, in “Species Filicum,” IV., p. 146, owing to the wide circulation of “Flora Novæ-Zelandiæ” the error has become generally circulated, and caused much confusion, especially in this colony.
The following is the synonomy of each so far as known to me:—
Hooker fil., Fl. Tasmaniæ, II., p. 149; Brown, Prodromus Nov. Holl., p. 149; Baker, Synopsis Filicum, p. 281; Hook. f., Handbook N.Z. Fl., p. 378.
N. decompositum, a. glabellum, Hook. fil,. Fl. Nov. Zel., II., p. 39, t. 79 (not of Cunningham).
N. decompositum, a. macrophyllum, Hook., Sp. Filicum, IV., p. 146.
N. pentangularum, Colenso, Filices Novæ Novæ-Zelandiæ, p. 9 (1845).
Aspidium decompositum, Spreng., Syst. Veg., IV., p. 109; Mueller, Fragmenta Phytographiæ Australiæ, V., p. 136.
Aspidium microsorum, Endl., Flora Norfolk Island, p. 9.
A. shepherdi, Kunze, Linnæa, XXIII., p. 259.
A. acuminata, Lowe, Filices, p.—. t. 11.
Hab. New Zealand, common on the banks of rivers.
Australia, Tasmania, Norfolk Island.
A. Cunningham, Comp. Bot. Mag., II., p. 367; Metten. Aspid., p. 69.
Nephrodium decompositum, β. pubescens, Hook. f., Fl. Nov. Zel., II., p. 39.
N. decompositum, β. microphyllum, Hook., Sp. Filicum, IV., 146.
Lastrea davalloides, Brack., Filices U.S. Exploring Expedition, p. 202.
Hab. New Zealand, common in forests.
Australia, Tahiti, Fiji Islands.