Plagiothecium

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.

Distribution

North America, Mexico, Central America, South America, Europe, Asia, Africa, Pacific Islands (New Guinea), Australia, Antarctica.

Discussion

Species ca. 90 (6 in the flora).

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.

Lower Taxa

Plagiothecium berggrenianum, Plagiothecium cavifolium, Plagiothecium denticulatum, Plagiothecium laetum, Plagiothecium latebricola, Plagiothecium piliferum

Key

1	Alar cells oval, quadrate, rectangular, or spheric; leaf margins broadly recurved	> 2
1	Alar cells rectangular; leaf margins plane or narrowly recurved	> 3
2	Stems complanate-foliate or sometimes julaceous; leaf apices acute to acuminate or rarely narrowly obtuse, seldom recurved; medial laminal cells 12-21 µm wide.	Plagiothecium denticulatum
2	Stems julaceous; leaf apices acuminate, usually recurved; medial laminal cells 6-12 µm wide.	Plagiothecium berggrenianum
3	Leaf apices abruptly contracted to long-filiform acumen.	Plagiothecium piliferum
3	Leaf apices not abruptly contracted	> 4
4	Leaves asymmetric, flat.	Plagiothecium laetum
4	Leaves symmetric, concave	> 5
5	Stems to 2 cm, 0.5-1 mm wide across leafy stem; leaves erect-spreading; medial laminal cells 4-10 µm wide; hydric habitats.	Plagiothecium latebricola
5	Stems to 4 cm, 1-4 mm wide across leafy stem; leaves erect or sometimes spreading; medial laminal cells 7-17 µm wide; mesic or somewhat xeric habitats.	Plagiothecium cavifolium