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Marsilea L.

Small aquatic or subaquatic ferns, rooting in mud in areas subject to periodic innundation. Rhizome creeping, the fronds well-spaced, also on short lateral branches, roots borne at the base of the fronds, growing tip covered with fine hairs, solenostelic, the cortex with many large air cavities. Fronds very long-stipate, with 2 opposite pairs of leaflets, leaflets radially arranged and floating on the water surface (when innundated), often bearing multicellular hairs; veins several times forked, radial, +/- free, or anastomosing occassionally or at the leaflet margin only; vernation circinnate. Sporangia of 2 types, borne in discrete sori in sporocarps; the sporocarps pedunculate, axillary or basally on the petiole, solitary or in groups, hard and woody, often hairy, globose to ovoid, 2 small projections often present at the end of the stalk, splitting when mature; the sori exindusiate, elongate, borne in 2 rows on a gelatinous ribbon (sporophore) that elongates as the sporocarp opens, receptacles in a single row, bearing a single apical megasporangium and 2 lateral microsporangis; sporangis with a solitary megaspore or 32 - 64 microspores, annulus lacking, opening by decay of sporangial wall. Spores trilete, globose, ornamented, the megaspores with a distinct beak.

A single species in Papuasia......M. crenata

Species in Papuasia

A single species in Papuasia...M. crenata