Krypt. Fl. Brandenburg 2: 918. 1906. -- Hypnum squarrosum Hedw., Spec. Musc. 281. 1801. -- Hylocomium squarrosum (Hedw.) Bryol. Eur. fasc. 49–51. 1852.
Plants to 25 cm long, in pale-green or yellowish-green wefts, loosely ascending to prostrate, irregularly branched. Leaves not plicate but so strongly squarrose as to be downwardly directed in distal 1/2, closely foliate, to 4 mm, 2–2.5: 1, ovate and rather abruptly contracted to the acumen. Line of leaf insertion encircling about 180 degree of stem circumference. Margins plane or nearly so throughout, not at all decurrent, entire to serrulate at base, serrulate to serrate above. Median cells smooth, 6–7 µm wide, linear, about 8–10: 1, somewhat thick-walled with lumen: wall ratio 5–6: 1, somewhat pitted. Median basal cells concolorous, broader and shorter than adjacent, more distal cells, thick-walled and with lumen: wall ratio about 2: 1. Alar cells somewhat differentiated in a rounded rather pellucid pocket, short-rectangular, 2–3: 1, pitted, to 15 µm broad. Costa double with forks separate from base, symmetrically inserted in center of leaf base, with both forks extending above the middle. Paraphyllia absent. Juvenile leaves orbicular, serrulate on margin, closely overlapping bud with first such leaf proximal to bud. Axillary hairs 5–7 celled, to 200 µm with two basal cells brown and short, mostly offset from leaf insertion. Stem cross-section with a small central strand, without a hyaloderm, with a well marked stereome of pachydermous, pigmented cells, and with inner cortical cells larger and mostly rather thick-walled. Rhizoids very rarely produced on old and prostrate stems or on bases of perichaetia, to 15 µm in diameter at insertion, arising from area immediately lateral to alar cells at leaf insertions, red-brown, monopodially branched with branches short, smooth and rather thick-walled.
Dioicous with male plants similar to females. Perichaetia on old, erect axes, with bracts to 2.5 mm long, clasping at base but abruptly contracted into the squarrose and narrow acumen. Seta to 2 cm long, erect, redddish brown, smooth. Capsule red brown, inclined and arcuate, neither sulcate nor strangulate. Urn to 2 mm, oblong and asymmetric, about 2: 1. Exothecial cells isodiametric to short rectangular, to 30 µm broad, in regular rows, with lumen: wall ratio 4–6: 1. Stomata phaneroporous, small and vertical pored, restricted to neck. Annulus present, not revoluble. Operculum conic, much shorter than urn. Exostome to 500 µm long, almost smooth but with light horizontal striae throughout, red-brown. Endostome segments lightly papillose, perforate along keel, about as long as exostome with basal membrane about 1/2 of total length. Cilia 1–3, lightly papillose, somewhat nodose. Spores green, smooth to very lightly papillose, to 15 µm.
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