9. Zygodon Hooker & Taylor, Muscol. Brit. 70, plates 3 [upper left], 21 [upper left]. 1818.
Plants small, in tufts or loose cushions. Stems erect to ascending, branches erect to ascending. Leaves loosely erect, irregularly twisted or curved around stem, sometimes undulate when dry, erect-spreading to squarrose-recurved when moist, oblong-lanceolate to linear-lanceolate, not rugose; base decurrent; margins entire, serrate or serrulate near apex; apex acute, usually apiculate; costa percurrent, ending near apex, or rarely excurrent; basal laminal cells subquadrate to rectangular; distal cells rounded-quadrate to rounded-hexagonal, 4-14 µm, smooth or densely multipapillose only over lumina, papillae 2-6 per cell, clavate; marginal cells not differentiated from basal. Sexual condition dioicous, autoicous, or synoicous; perichaetial leaves little different from stem leaves. Seta 3-13 mm. Capsule long-exserted, elliptic-oblong to fusiform, strongly 8-ribbed entire length, not constricted below mouth; stomata superficial; peristome double, single, or absent; exostome teeth 8, or 16 partially connate in 8 pairs, papillose; endostome segments 0, 8, or 16. Calyptra cucullate, conic, smooth, naked or rarely hairy, not plicate, covering distal portion of capsule. Spores isosporous.
Species ca. 90 (5 in the flora): North America, Mexico, West Indies, Central America, South America, Europe, Asia, Africa, Pacific Islands (New Zealand), Australia.
Many species of Zygodon rarely produce sporophytes, and taxa are delimited on characters derived exclusively from the gametophyte. The genus is largely pantropical with several widespread temperate species. None of the species are found farther north than 60± Nlatitude. The leaves are keeled; the basal laminal cells are usually pale yellow; the capsules are 1-2 mm; and the spores are 11-22 µm.