Trans. Linn. Soc. London12: 561. 1819 ,
North America, e Asia (including Siberia).
Species 4 (1 in the flora).
Lyellia is a small genus with a disjunctive distribution, with representatives occurring in the Himalayas and eastward, and a single species, L. aspera, at high latitudes in arctic America and eastern Asia. The capsules are strongly dorsiventral, resembling those of Dawsonia in shape, but without a peristome. The flattened columella apex projects from the center of the disc like a stopper in a wash basin (Gary L. Smith 1971, fig. 25); the epiphragm remains embedded in the operculum. The hypophysis has prominent stomata, the guard cells surrounded by a ring of thin-walled, hyaline subsidiary cells, which are sharply differentiated from the surrounding cells of the exothecium.