Isoetaceae

Small, submerged or emergent aquatic plants, evergreen or decidiuous, occurring in aquatic or seasonally wet habitats. Rhizome short, corm-like; rootlets dichotomously branched, arising from a basipetal growing point beneath the rhizome. Leaves in a rosette, flat or cylindrical, grass-like, leaf base spathulate with a membranous margin and a delicate triangular ligule on upper surface where leaf narrows. Sporangia sessile, ovoid or globose, initially embedded in the adaxial surface of the leaf base below the ligule, partially or entirely covered by a thin membranous outgrowth (velum), heterosporous.