EPHEMERACEAE

Plants minute, with persistent, but sparse to abundant protonemata. Stems very short, erect, undivided, central strand lacking; rhizoids basal, smooth. Leaves few, usually forming rosettes, larger ones linear-lanceolate to lanceolate, acuminate, entire to serrate; costae single and well-developed to absent; leaf cells unistratose, thin-walled, smooth or scindulose, upper cells rhomboidal to oblong-rhomboidal, lower cells broader, more or less oblong, pellucid. Synoicous, dioicous or rhizautoicous. Sporophytes solitary, terminal. Setae lacking or nearly absent. Capsules more or less sessile, immersed, ovoid or globose, at times apiculate, cleistocarpous, irregularly dehiscent, or stegocarpous by means of a median line of cells; exothecial cells more or less oblong, thin-walled; stomata phaneroporous with two guard cells or absent; columellae resorbed during maturation; peristome absent. Calyptrae mitrate, smooth or scindulose and deciduous, or minute, usually consisting of the unaltered remains of archegonia.