6. ALSOPHILA, R. Br.
Usually tree-ferns, but in some species the trunk is short or absent. Fronds large, 2–3-pinnate, very similar to those of Cyathea or Hemitelia. Veins of the segments forked or pinnately divided. Sori dorsal, globose, situated upon a vein or at the fork of a vein; receptacle more or less elevated, pilose. Indusium altogether wanting. Sporangia numerous, sessile or nearly so, often mixed with hairs, bursting transversely; ring somewhat oblique, complete.
Species about 120, mostly tropical, nearly half of them from America, the remainder scattered through tropical Asia, Malaya, and the Pacific islands, with a few in Africa. The single New Zealand species is endemic.
1. A. Colensoi, Hook. f. Fl. Nov. Zel. ii. 8, t. 73.—Caudex long, prostrate and rooting, seldom more than 6–8 in. in circumference, rarely erect or ascending at the tip and attaining a height of 3–5 ft. fronds 2–5 ft. long, ¾–2 ft. broad, 2–3-pinnate, broadly ovate-lanceolate, acute, membranous, yellowish-green or reddish-brown. Stipes short, densely covered at the base with pale subulate scales 1 in. long, upper portion, together with the rhachis and costæ, more or less thickly clothed with fulvous or reddish-brown hairs intermixed (especially on the under-surface) with pale tumid scales. Primary pinnæ 9–15 in. long, 2–3½ in. broad, oblong-lanceolate, acuminate; secondary 1½–2 in. long, about ½ in. broad, pinnatifid above, pinnate at the base. Segments oblong, obtuse, obtusely serrate; veins simple. Sori copious, situated on the middle of the veins.—Handb. N.Z. Fl. 350; Hook. and Bak. Syn. Fil. 40; Thoms. N.Z. Ferns, 30; Field, N.Z. Ferns, 48, t. 3, f. 4.
North Island: Mountains of the interior, from Hikurangi and Mount Egmont southwards. South Island: Not uncommon in hilly and subalpine forests throughout. Stewart Island: Mount Anglem, Kirk! Usually between 2000 and 4000 ft., but descends to low levels in the south of Otago.
For some interesting remarks on the mode of growth of this species, see Mr. Field's "New Zealand Ferns," quoted above; also a paper by the same author in the "Journal of Botany" for 1878, p. 365.
7. DICKSONIA L'Herit.
Usually tree-ferns, but in some species the caudex is short or absent. Fronds large, 2–3-pinnate. Stipes smooth or muricate. Veins pinnately forked, veinlets always free. Sori near the margin of the frond, globose, placed on the apex of a veinlet; receptacle more or less elevated. Indusium distinctly 2-valved, the upper valve continuous with the margin of the frond and usually similar to it in texture, consisting of an incurved or concave lobule; lower valve membranous or coriaceous. Sporangia numerous, sessile or nearly so, bursting transversely; ring oblique, complete.
