Monographs Details: Grimmia orbicularis Bruch
Description:Species Description - Stems 10-20 mm long or rarely more. Leaves imbricate, keeled, usually ± oblong-lanceolate, usually obtuse, up to 1.4 mm long (exclusive of denticulate hair points up to 1 mm long); margins recurved, usually on both sides, unistratose or rarely bistratose in spots; costa with 2 guide cells at base; cells unistratose, about 10 µm, quadrate to rounded or irregular, ± sinuose, becoming larger and distinctly sinuose at midleaf; basal cells elongate and sinuose adjacent to the costa, quadrate at the margins. Autoicous. Perichaetial leaves 1.6-2 mm long, with hair points up to 2.6 or even 3 mm long. Setae 1.5-2.5 mm long, arcuate when moist; capsules emergent, about 1 mm long, ovoid, ribbed when dry; annulus deciduous, of 2-3 layers of cells; operculum bluntly low-conic; peristome teeth red-brown, cleft and cribrose. Spores 9-12 µm, smooth. Calyptrae cucullate.
Distribution and Ecology - Often on limestone, up to about 1300 m alt.; Sonora; reported from Distrito Federal (Cardot, 1911).—Mexico; southwestern United States; Europe; Asia; Africa; South America; Australia.
G. orbicularis Bruch ex Wils., Engl. Bot. Suppl. 4: pl. 2288. 1844.
Guembelia orbicularis (Bruch ex Wils.) Hampe ex C. Mull., Syn.
Muse. Frond. 1:775. 1849.
Grimmia orbicularis differs from G. pulvinata in having usually unistratose leaf margins, sinuose-walled basal cells, low opercula, and cucullate calyptrae.