Plagiobryum

Plants small to large, as turf or ± caespitose clumps, reddish brown to green or whitish to silvery green with pink tinge. Stems 0.3–1.5(–2) cm, julaceous or not, usually highly branched proximal to apex by sterile subperichaetial innovations; rhizoids usually many, micronemata present especially near base. Leaves of main shoot axes erect-spreading to appressed, spreading when moist, broadly ovate to lanceolate, flat to concave, 0.7–1.4 mm, larger toward stem apex; base usually slightly decurrent; margins plane or recurved, entire, 1-stratose, limbidium absent; apex ± reflexed; costa subpercurrent to short-excurrent, guide cells absent; alar cells similar to juxtacostal cells; laminal areolation heterogeneous; proximal laminal cells rectangular in older leaves, 2–5:1; medial and distal cells rhombic to rectangular, 2.5–5:1, walls firm, not pitted or porose. Specialized asexual reproduction absent. Sexual condition dioicous; perigonia and perichaetia terminal; perigonia budlike, leaves more ovate, more abruptly acuminate than perichaetial leaves; perichaetial leaves usually enlarged. Seta usually single, slightly curved to cygneous, often geniculate. Capsule horizontal to pendulous, clavate, gibbous, distinctly zygomorphic, 2–14 mm; hypophysis well developed; operculum small, mammillate to short-conic; peristome double; exostome yellow to brown, teeth narrow-lanceolate, shorter than endostome; endostome loosely adherent to exostome, basal membrane high, segments narrow, perforations narrow, cilia rudimentary. Spores adherent in tetrads, at least until maturity, 26–42 µm, densely papillose, yellowish to greenish brown or brown.

Distribution

North America, Central America, Europe, Asia, Africa, Pacific Islands (New Zealand).

Discussion

Species 9 (2 in the flora).

Plagiobryum is easily distinguished when fruiting by the large, gibbous, and distinctly zygomorphic capsules. The stem is soft, erect, and slender, and in transverse section has cortical cells smaller than interior cells, walls thicker, in one to three layers, and central strand present; the rhizoids are red to red-brown. The innovations have smaller, more ovate leaves than the fertile stems. The marginal laminal cells are usually somewhat longer and narrower, in 1–3 rows, but do not form a distinct border. The capsules are furrowed when dry, narrowed to oblique mouths, and have a well-developed peristome with unbordered exostome teeth; the spores are elliptic.

Selected References

None.

Lower Taxa

Plagiobryum demissum, Plagiobryum zieri

Key

1	Plants whitish or silvery green, usually with pink tinge; innovations julaceous; leaves of innovations imbricate, broadly ovate to nearly circular; margins plane; exostome 0.8-0.9 times endostome length; spores separate at maturity.	Plagiobryum zieri
1	Plants red to reddish brown; innovations not julaceous; leaves of innovations erect to erect-spreading, ovate-lanceolate to lanceolate; margins recurved; exostome to 1/2 endostome length; spores released in tetrads.	Plagiobryum demissum