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Rheopteris Alston

Low to middle height epiphytes of moderate size, the rhizome creeping, fleshly, sparsely branched with the fronds spaced and borne more or less in a single rank, vasculature an amphiphloic siphonostele, rhizome and base of stipe bearing dense scales, the sacles thin, clathrate, rounded and more or less peltate at the base, long-tapering apically, margin spinulose. Stipe (and rachis) terete abaxially, rounded and deeply sulcate adaxially, glabrous except at the base, 2 lateral vascular bundles enter the base of the stipe and continue for the length of the frond; upper stipe and rachis with 2 very dark green bands of chlorophyllous tissue in the 2 ridges either side of the sulcus. Frond pinnate, lamina narrow oblong-elliptic, the upper pinnae tapering gradually into a narrow pinnatifid tip, the lower pinnae slightly reduced, decurrent into the adaxial ridges on the rachis, the pinna-stalk slightly grooved and this groove decurrent into the main rachis groove, the pinnae +/- trapezoid, dimidiate, margins cartilaginous, texture thick-chartaceous to thin-coriacious, veins simple or once-forked, free, teminating in a translucent swelling just short of the margin in a crenulation. Sori circular, terminal on the vein ends, 3-7 along the acroscopic margin, often with 1-3 along the basiscopic margin as well, exindusiate, sporangia protectedby numerous paraphyses attached at the base of the sporangium stalks, the apical cells clavate and curved, darker coloured; sporangia on a 3-seriate stalk, annulus longitudinal, interrupted, of c.18 thickened cells. Spores trilete, more or less spherical, translucent, appearing almost smooth.

Species in Papuasia

A monotypic genusR. cheesemaniae

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