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Amphineuron Holtt.

Terrestrial ferns of moderate to large size. Rhizome an erect or ascending caudex, sometimes long-creeping, radially symmetric, dictyostelic, bearing narrow scales with acicular hairs. Fronds long-stipitate, the stipe with 2 vascular bundles at the base uniting upward into a single U-shaped vascular strand, minutely hairy, scaly at the base, lamina pinnate with pinnately most deeply lobed pinnae, margin entire, basal pinnae not reduced but narrowed at the base, less commonly 1-2 pairs of irregularly shaped and placed pinnae may occur below the regular ones, midribs of pinnae grooved above, but grooves not confluent with rachis groove, aerophores at bases of pinnae not swollen, abaxial surface with unicellular acicular hairs and various small, stalked, spherical to pyriform glands, sometimes large resinous sessile glands, veins in a pinnate group in each pinna-lobe, basal veinlets either free to the margin or terminating at the sinus membrane or anastomosing to form an excurrent vein terminating at the sinus membrane (sometimes not consistent for a single frond), remaining veinlets simple, free, terminating in the margin above the sinus membrane, sinus membrane often with a prominent tooth. Sori round, mostly indusiate, the indusium mostly with hairs and/or glands, medial to near the ends of the veins, sometimes confined to pinna-lobes; sporangia on a short 2-seriate stalk, the stalk bearing a glandular hair, body of sporangium normally lacking hairs or glands, annulus longitudinal interrupted. Spores monolete, opaque, usually dark, irregularly rugulose or with irregular, thick, +/- branched ridges.

Key modified ex Holttum 1981, F1. Males. ser. 2, 1:544.

Species in Papuasia

1a. Indusium rather large, persistant; lamina thin, veins slender, slightly prominent on both sides
Indusium small, almost hidden by sporangia at maturity of sorus, or apparently lacking; lamina firm, veins not prominent on either surface
2a. Caudex long-creeping; pinnae lobed 1/2 way to costa or less deeply; apex of frond +/- pinna-like
A. terminans
Caudex short-creeping or erect; pinnae lobed more than 1/2 way to costa; apex of frond not pinna-like
3a. Pinnae lobed to 1 mm from costa or more deeply; basal veins quite free or uniting to form very short excurrent veins
Pinnae lobed less deeply; basal veins anastomosing to form a distinct excurrent vein on most parts of the frond
A. opulentum
4a. Basal veins not meeting at the sinus; sori in slight depressions
A. immersum
Basal veins meeting just below the sinus, sometimes forming a short excurrent vein; sori not immersed
A. subattenuatum
5a. Hairs more than 0.5 mm long present on both surfaces of the costa; stipe and abaxial surface of rachis bearing scales throughout
A. distinctum
All hairs on costa very short; scales confined to base of stipe
6a. Many glandular hairs on lower surface between veins, some spherical, some +/- elongate; similar hairs also on indusia
A. ceramicum
Glandular hairs less abundant, always spherical, tending to collapse and to form resinous patches or to disappear on drying
A. pseudostenobasis