Mesophlebion Holtt.

Terrestrial ferns of moderate to large size. Rhizome a short-creeping, sometimes elongate, radially symmetric caudex, dictyostelic, bearing narrow, rigid (but not spine-like), basally attached scales with short, superficial and marginal, acicular hairs, similar hairs at base of stipe. Fronds long-stipitate, the stipe with 2 vascular bundles at the base uniting upward into a single U-shaped vascular strand, lamina pinnate (rarely simple or partly bipinnate) with mostly deeply pinnately lobed pinnae, aerophores often distinctly swollen in fresh material (collapsing on drying), basal pinnae not reduced but narrowed towards their asymmetric bases, margin entire, midribs of pinnae grooved above, but the grooves not confluent with rachis groove, abaxial surface with small, narrow scales of various stages of reduction and unicellular acicular hairs on costae, costules and veins, abaxial surface of costules sometimes with large, sessile, red glands, adaxial surface with hairs on costae only, veins in a pinnate group in each pinna-lobe, basal basiscopic vein arising from costa below insertion of costule, basal veinlets of each group free and terminating either side of the sinus membrane, remaining veinlets simple, free, terminating in the magin above the sinus membrane. Sori round, nearly always indusiate, the indusium thin, sometimes small, medial on each vein; sporangia on a short 2-seriate stalk, the stalk bearing a sessile or hair-stalked large red gland, no hairs or glands on body of sporangia, annulus longitudinal interrupted. Spores monolete, mostly with a thin continuous wing and a few cross-wings, or sometimes papillose without wings.

Key modified ex Holttum 1981, F1. Males. Ser. 2, 1:377.

Species in Papuasia

1a. Indusium firm, glabrous, covering the sorus almost to maturity; fertile pinnae lobed to 1-1.5 mm from costae M. beccarianum
Indusium small, not covering developing sori, or +/- hairy; fertile pinnae lobed less deeply 2
2a. Fertile pinnae lobed to 2 mm from costae; indusia small, firm, glabrous M. rufescens
Fertile pinnae lobed less deeply; indusia usually with some hairs, thin and almost obscued by sporangia if small 3
3a. Fronds rarely dimorphic; pinnae thin, rarely more than 2 cm wide; indusia always conspicuous, firm, bearing a variable number of short hairs; costa beneath rather sparsely hairy M. chlamydophorum
Fronds usually ddimorphic; pinnae rigid, fertile to 3 cm wide, sterile to 4 cm wide; indusia varied in size, thin and shrivelled when dried; costa closely hairy beneath M. crassifolium