23. Grimmia unicolor Hook. in Grev. 厚边紫萼藓 hou-bian zi-e xian
Scott. Crypt. Fl. 3: 123. 1825. Dryptodon unicolor (Hook.) Hartm., Handb. Skand. Fl. (ed. 3), 272. 1838. Type. United Kingdom: “Rocks near Bachnagain, the Honourable D. Ogilvie’s hunting lodge at the head of Clova” (isotype BM).
Plants medium-sized, up to 3 cm high, yellowish green above, dark green to blackish below, in dense tufts. Stems erect, regularly branched from innovations above, with well developed central strand in cross section. Leaves erect and imbricate when dry, erect-spreading when moist, concave and somewhat cucullate, rounded at the apex, not keeled, 1.7–2.2 mm long, oblong-lanceolate, narrowed from a broader base to lanceolate, muticous, narrowly obtuse; margins erect, entire; costa flattened, subpercurrent, ending shortly below the apex, without distinct small cells in cross section; upper cells irregularly rounded, obscure, 5–7 µm wide, bistratose or sometimes tristratose in places at margins, with strongly incrassate, sinuose walls; basal marginal cells rectangular, 18–23 µm × 6–9 µm, with straight walls; basal juxtacostal cells elongate, 34–46 µm × 5–7 µm, with thick, somewhat sinuose walls. Dioicous. Perichaetial leaves similar to the upper stem leaves in shape, but larger. Setae yellowish to yellowish brown, straight, ca. 2–3 mm long; capsules exserted, erect and symmetric, oblong-cylindrical, 1.5 mm long, smooth when moist, slightly wrinkled-striate when old and dry; exothecial cells variable in shape, usually elongate-hexagonal with thin, straight walls; stomata present at base of urns; annuli differentiated, composed of 2–3 rows of thick-walled cells; opercula concave-conic, with a short beak; peristome teeth lanceolate, reddish brown, imperfectly divided into 2 segments in upper part, perforate in the middle, outer surface densely papillose above, sparsely papillose below, inner surface papillose throughout. Calyptrae mitrate, lobed at base, often split further up on one side. Spores 8–12 µm in diameter, yellowish, smooth to finely papillose.