1. Plagiothecium Schimper in P. Bruch and W. P. Schimper, Bryol. Europ. 5: 179, plates 494-506. 1851. • [Greek, plagios, oblique, and theke, case, alluding to capsule orientation].
Stereodon sect. Plagiothecium (Schimper) Mitten
Plants dark green to yellow-green, glossy or sometimes dull. Stems 2-6(-8) cm, 0.5-4 mm wide across leafy stem. Leaves 0.7-4 × (0.2-)0.4-2 mm; alar cells spheric, oval, quadrate, or rectangular, in 1-8 vertical rows, region triangular, or auriculate and oval; basal laminal cells shorter, broader than medial; medial cells 36-180 × 3-21 µm; apical cells often shorter. Specialized asexual reproduction by 2-7-celled propagula borne on branched stalks in leaf axils or in clusters without stalks on abaxial leaf surface. Seta yellow or orange to red-brown. Capsule yellowish, orange-brown, reddish, light brown, or dark red when mature, oblong to ovoid, smooth to striate, often wrinkled at neck, often contracted below mouth when dry; annulus differentiated; endostome cilia 1-3, usually as long as segments or nearly so, nodulose, rarely rudimentary or absent.
Species ca. 90 (6 in the flora): North America, Mexico, Central America, South America, Europe, Asia, Africa, Pacific Islands (New Guinea), Australia, Antarctica.
Plagiothecium is a genus of terrestrial habitats in coniferous and deciduous woods, on rotten logs, stumps, bases of trees, humus and soil, frequently overlying acidic cliffs and boulders, sometimes in swamps and marshes, in temperate, boreal and Arctic regions, and in the tropics at high elevations.
SELECTED REFERENCES Ireland, R. R. 1969b. A Taxonomic Revision of the Genus Plagiothecium for North America, North of Mexico. Ottawa. Ireland, R. R. 1986. Synopsis of the genus Plagiothecium for North America. Lindbergia 12: 49-56. Ireland, R. R. 1987. Scanning electron microscope study of the spores of the North American species of Plagiothecium. Mem. New York Bot. Gard. 45: 95-110.