Page:Manual of the New Zealand Flora.djvu/965

Asperella.] leafy, 10–30 in. high. Leaves 3–9 in. long, $1⁄15$–⅛ in. broad, flat or involute, striate, smooth or nearly so; sheaths smooth or puberulous; ligules short. Spike 3–6 in. long, slender, of 15–30 spikelets; rhachis flat, flexuous, scabrid on the edges. Spikelets pale-green, about ⅓ in. long, 1–2-flowered. Two outer glumes always present, reduced to linear-subulate bristles about three-quarters the length of the lower flowering glume, subequal, erect, channelled, scabrid. Flowering glumes lanceolate, faintly 3–5-nerved, rounded on the back, quite smooth, unequally 3-toothed at the apex, the middle tooth produced into a short scabrid mucro. Palea rather shorter than the glume, keels smooth or minutely ciliolate.

Perennial or very rarely annual plants, usually herbaceous but sometimes arboreous (tree-ferns). Stems generally reduced to a rhizome, which may be short and tufted, or long and creeping or climbing; or, in the case of tree-ferns, produced into an erect caudex or trunk. Leaves (fronds) either crowded at the end of the rhizome or distantly placed along it, continuous with the rhizome or jointed to it, sometimes simple and entire, but usually more or less deeply pinnately lobed or divided and frequently repeatedly so, more rarely dichotomously branched; always circinate in vernation with the exception of the Ophioglossaceœ. Spore-cases or sporangia usually arranged in groups (sori) on the under-surface or margins of the fertile fronds, which are either similar to the sterile fronds, or narrower and more contracted, the divisions sometimes becoming linear and spike-like. Sori very various in size and shape and position, naked or covered when young by the recurved margin of the frond or by a special involucre (indusium). Sporangia many or rarely few in a sorus, often mixed with jointed hairs or scales, stalked or sessile, usually furnished with a complete or incomplete ring or annulus, dehiscing by a transverse or vertical slit, free or rarely coherent into a compound sporangium (synangium). Spores numerous, bilateral or tetrahedral.

Ferns constitute one of the largest and most generally distributed of the families of plants, and are found in all quarters of the world, although most abundant in moist climates. It is difficult to estimate the number of species, on account of the divergent views of authors, but they cannot be less than 3500. In the subjoined account of the New Zealand species I have adopted the