Studies in the family Thelypteridaceae V. The genus Pneumatopteris Nakai

I re-described this genus in Blumea 19 (1971) 42. The principal characters there enumerated are: rhizome-scales broad, thin, with marginal hairs (some bearing mucilage glands) but rarely superficial hairs; lower pinnae, usually several pairs, reduced, the transition to reduced pinnae abrupt or gradual; aerophores at bases of lower pinnae ± swollen and white on young fronds, sometimes much elongate; pinna-lobes with cartilaginous margins which are often toothed at the ends of veins; veins usually anastomosing but free in some species which have deeply lobed pinnae; lamina ± pustular when dried; lower surfaces never densely long-hairy, sometimes with short acicular or capitate hairs; sessile spherical glands lacking on lamina, indusia and sporangia; body of sporangium often bearing club-shaped or capitate hairs, rarely setae; on stalk of sporangium a hair of 3 or 4 cells, terminal cell enlarged but not spherical; spores light brown with many small thin ± quadrate wings, thus spinulose in aspect. The majority of species here included in this genus conform to all the above characters, but there are some species which differ by showing one or two (rarely three) of the following characters: basal pinnae not or little reduced; scales on bases of stipes elongate and bearing many superficial hairs; spores with a ± continuous wing and anastomosing cross-wings. Almost all these aberrant species have distinctly pustular lower surface, and have the usual accompanying characters of rather thick veins and cartilaginous edges of pinna-lobes.