Riellaceae

Ephemeral, aquatic on mud or rarely terrestrial well above water inundation (not in Victoria), monoicous or dioicous with female and male plants of similar size or rarely males with an additional thallose wing (not in Victoria). Multicellular scale-like gemmae often produced on abaxial surface of stem. Plants comprising a simple or sparingly furcate axis that gives rise to prominent dorsal thallose wing or rarely two wings (not in Victoria), and two lateral and two abaxial rows of much smaller leaf-like scales, bright green, males sometimes becoming chestnut brown with maturity; thallose wing rectangular in outline, falcate apically, erect, unistratose, without air-chambers or pores, undulate to ruffled; lateral and abaxial leaf-like scales triangular, oblong, ligulate or filamentous, unistratose; thallus cells quadrate to hexagonal, several with a single spherical rough oil body scattered throughout. Rhizoids present, smooth, colourless. Antheridia enclosed within oblong or flask-shaped perigonial chambers along wing margin, in wing sinuses or rarely between two wings on adaxial stem (not in Victoria). Sporophyte enclosed within pseudoperianth along the axis and each positioned on the opposite side of the dorsal wing than the last or rarely between two wings (not in Victoria); pseudoperianth subglobose, ovoid or pyriform, sessile or stalked, with (not in Victoria) or without longitudinally oriented ribs; involucre absent. Seta short. Capsule globose to ovoid, cleistocarpous, unistratose, with a bulbous foot; elaters absent. Spores globose, hemispheric to tetrahedral, spinose with or without a faint triradiate mark on proximal face, red- or dark brown, shed singly.