22. Bryum knowltonii Barnes 沼生真藓 zhao shen zhen xian
Bot. Gaz. 14: 44. 1889. Ptychostomum knowltonii (Barnes) Spence, Phytologia 87: 21. 2005. Type: Canada.
Plants small, 5–10 mm high, yellowish green to brown, in dense tufts. Stems usually branched, with rhizoids at base. Leaves rather dense in the upper part of stems, erect or variously twisted when dry, spreading when moist, ca. 2.0–2.5 mm long, elliptical to ovate, acute or shortly acuminate, not decurrent at base; margins entire, recurved or slightly recurved at base; costae nearly percurrent or percurrent, reddish below; upper and median leaf cells oblong-rhomboidal, ca. 3–4׃1 (length׃width), thick-walled, becoming narrower near the margins, but borders not differentiated. Synoicous. Setae 12–25 mm long; capsules pendulous, ca. 1.5–2.5 mm long, broadly pyriform; neck short; opercula conic, shortly apiculate; exostome teeth yellowish brown, reddish at base, densely papillose; endostome segments yellowish, perforate; basal membrane ca. 1/2 the height of the teeth; cilia short, 2–3 or rudimentary. Spores 22–24 µm in diameter, minutely papillose.