Hymenolomataceae. Genus Hymenoloma
1. Lamina unistratose; cuticular papillae conspicuous; leaves 2.5-3.0 mm long, strongly crisped when dry; alar cells conspicuously differentiated —
1. H. crispulum
A common species in the north and high mountains almost throughout Russia. It can be recognized in many cases by its numerous capsules. Thin setae, rather thin, membranaceous urn walls with tiny longitudinal riffles, as well as strongly crispate leaves are distinctive features of the species.
— Lamina partially bistratose above; cuticular papillae inconspicuous; leaves 2.0-2.5 mm long, curved inwards when dry; alar cells usually not or weakly differentiated —
2. H. mulahaceni
It is not always easy to recognize this plant as a species of Hymenoloma because cuticular papillae may be absent or inconspicuous. Membranaceous capsule texture and bistratose leaves are distinctive features of the species. The species occurs in Russia in dry and cold high mountains. Pluricellular ellipsoid gemmae in the leaf axils are reported for this species, but they were never observed in Russian collections.