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Acrostichum L.

Erect terestrial or subaquatic ferns of medium to large size, mostly in brackish, sometimes freshwater, swamps and marshes. Rhizome woody, short, stout, erect, dictyostelic with medullary strands, bearing broad thick scales attached by a broad base, often with aerenchymatous strut-roots. Fronds long-stipitate, the stipes adaxially grooved, with a single U-shaped vascular strand, the lamina simply pinnate, the pinnae alternate, stalked, large, lanceolate or narrow-oblong, entire, thick-coriaceous, the apical pinnae similar to the lateral, a few reduced glandular pinnae that function in young fronds represented by short residual spines sone the stipe, costa prominent, no main veins evident, venation oblique, closely anastomosingto form many series of irregular but +/- uniform, narrow areoles, without included free veinlets. Sporangia acrostichoid, densely covering all or the apical half of the abaxial surface of the apical few pinnae, the fertile portions slightly contracted; exindusiate, paraphyses numerous, apically clavate or variously lobed (? = abortive sporangia), annulus longitudinal, interrupted, of 20-22 thickened cells. Spores trilete, pale, minutely tuberculate.

Species in Papuasia

1a. Apex of sterile pinnae abruptly rounded or truncate and shortly tipped; young fronds strap-like... A. aureum
Apex of sterile pinnae narrowly acuminate; young fronds broadly lanceolate... A. speciosum