Marsileaceae

Abstract

Small or even minute ferns of periodically moist to flooded places. Stem slender, creeping, often branching, with a radial solenostele, with little sclerenchyma and with air canals, bearing septate hairs, often glabrescent. Leaves circinate in bud, septate-hairy when young but often glabrescent at maturity, borne in two dorsal rows, usually remote; petiole non-articulate, terete, green, with one V-shaped vascular bundle. Lamina simply pinnate, the segments two or four, so close as to make the lamina appear palmate, or lacking. Sori borne in globose to ellipsoid, firm, at least initially septate-hairy, stalked sporocarps with very firm wall, these inserted on simple or sometimes branched stalks on the lower part or the base of the petiole or on the stem near the petiole base, dehiscing with two valves; each sporocarp with at least two sori each containing mega- and microsporangia. Annulus wanting. Spores trilete, of very different size, one in each megasporangium, many in each microsporangium. Microspores free from each other. Gametophyte strongly reduced, not becoming free from the spore.