Syntrichia princeps Mitten 1859

The synoicous condition of Syntrichia princeps is diagnostic if present, but otherwise one must rely on wider basal leaf cells, costal hydroids, and the stem central strand to separate this species from S. ruralis, S. papillosissima, and S. norvegica. The more acute leaves with cells generally smaller, and costa reddish and serrulate separate it from S. obtusissima.

Stems 5-20 mm. Leaves usually in distinct whorls, infolded, somewhat contorted, and weakly to strongly twisted around the stem when dry, wide-spreading to slightly recurved when moist, concave, spatulate, 2-4 × 1-1.5 mm; margins revolute in the proximal ¹/2-³/4, entire; apices acute or sometimes truncate; costa excurrent into a long, serrate, hyaline awn (reddish at base), often strongly papillose abaxially and serrulate near the apex because of projecting cell ends, red; basal cells abruptly differentiated, long-rectangular, 45-80 × 20-30 µm, short-rectangular to quadrate at the margins; distal cells quadrate to hexagonal, 12-17 µm, slightly bulging, bearing 4-6 papillae per cell. Specialized asexual reproduction absent. Sexual condition synoicous (apparently rarely dioicous). Seta red, 10-18 mm. Capsule brownish red, 3-4 mm, slightly curved, with a distinct neck; operculum 1.5-2 mm, brown; peristome ca. 1.5 mm, the distal divisions twisted about 2 turns, red, the basal membrane white, ¹/2-²/3 the total length. Spores 9-13 µm, papillose.

Plants medium-sized to large, 2.0–5.0 cm high, dark green to reddish brown, in dense tufts. Stems erect, simple or irregularly branched, radiculose at base; central strand present. Leaves appressed or somewhat contorted-curved when dry, spreading when moist, oblong-ligulate to spathulate, obtusely acute at apex, upper lamina broadly channeled or keeled, weakly sheathing at base; margins often recurved, crenulate by projecting papillae; costa rather stout, reddish brown, excurrent, ending in a long, hyaline awn, denticulate on the back or at tips; upper leaf cells quadrate to hexagonal, each cell densely covered with several C-shaped papillae; basal cells distinctly differentiated, rectangular, thin-walled, smooth, hyaline or reddish. Autoicous (synoicous). Setae elongate, straight, reddish; capsules erect, cylindrical; peristome teeth linear, twisted, papillose; basal membrane high.

Distribution: China, India, Himalayas, Turkey, Europe, North and South America, Africa, and Australia.

Habitat: on rocks.

Tortula princeps De Notaris, Mem. Reale Accad. Sci. Torino 40: 288. 1838

Barbula princeps (De Not.) C. Müll., Syn. Musc. Frond. 1: 636. 1849.