Ricciocarpus natans

Ricciocarpus natans (ly.) Corda, in Opiz, Beitr. 651. 1829
Riccia natans L. Syst. Nat. ed. 10. 1339. 1759.
Riccia capillata Schmidel, Ic. PI. 276. 1797.
Riccia lutescens Schw. Specim. FI. Am. Sept. 26. 1821.
Riccia velutina Wilson; Hook. Ic. PI. pi. 249. 1840.
Ricciocarpus velutinus Stephani, Bull. Herb. Boiss. 6: 758. 1898.
Floating thalli or their segments obcordate or flabelUform, mostly 4-10 mm. long, and 4-9 mm. wide, dark-green, often violet or brownish on margins and lower surface; terricolous conditions forming rosettes 25-35 mm. in diameter or irregularly gregarious and having oblong, obovate, or obcuneate segments, these mostly 2-4 mm. wide; apices obtuse or subtruncate and emarginate, or cordate; margins acute, becoming more obtuse and buUateundulate in terricolous forms; capsules slightly protuberant above, crowded in 1-3 series along the median line, of rather infrequent occurrence, being found chiefly in early summer in forms inhabiting transient ponds; spores dark-brown at maturity, 42-57 ju in maximum diameter, angular, rather narrowly and obscurely dentate-alate, almost uniformly papillateareolate on all faces, the areolae poorly defined, mostly 7-8 /i broad, obscure with age, the papillae numerous, obtuse or truncate, 1-4 ix long.
Type locality: Hadley, Suffolk, England.
Distribution: Cosmopolitan. Ontario to British Columbia; San I^uis Potosi; Cuba.