Hydatellaceae

Abstract

Minute aquatic or subaquatic herbs, annual or rarely perennial. Roots numerous, unbranched. Stem very short, branching to form a leafy tuft, often with minute multicellular hairs in the leaf axils. Leaves basal, linear to filiform, lacking distinct sheaths or ligules, 1-veined, glabrous. Inflorescence a heterogamous or homogamous capitulum, terminal, sessile, or scapose, with an involucre of 1–4 pairs of opposite, membranous, glabrous, 1-veined bracts often forming an apparent whorl. Flowers unisexual, numerous, minute, lacking perianth and bracteoles. Male flower a solitary stamen; anther elliptic to linear, basifixed, bithecate, tetrasporangiate, dehiscing by lateral slits. Female flower a solitary unicarpellate pistil; ovary stalked, unilocular, utriculate, with (Trithuria) or without (Hydatella) 3 prominent ribs; ovule 1, pendulous, anatropous; stigma terminal, sessile, with 2-10 hairs each a single row of distended cells. Fruit membranous, dehiscent or indehiscent. Seed solitary, ovoid; embryo minute, peripheral, covered by an operculum; endosperm replaced by starchy perisperm.

Deceased.