Orthotrichum Moss

Orthotrichum pusillum Mitt. Jour
Linn. Soc. 8: 25. 1864.
Orthotrichum psilocarpum T. P. James, Trans. Am. Phil. Soc. 13: 110. 1869.
Plants small, blackish-green, 5 mm. high or less, in loose patches; upper leaves larger than the lower, broadly oblong-lanceolate to oblong-lingulate, narrowly to broadly obtuse, keeled, some or all denticulate at the apex, 1.5-2.5 mm. long, the margins strongly revolute; upper leaf-cells irregularly rounded, incrassate, about 15 ^ in diameter, papillose, the basal shortly rectangular, 2-4 times as long as broad, shorter on the margins; monoicous; capsules almost sessile, nearly or quite immersed, subglobose to ovoid, short-oblong when dry, smooth except occasionally when very old and dry, never ribbed, whitish, the urn about 1.6 mm, long; calyptra plicate, naked; exothecial cells thin-walled except a few rows around the mouth of the capsule, not otherwise noticeably differentiated; stomata immersed, about the middle of the capsule; annulus present; operculum convex-umbonate; peristome-teeth 16, densely and coarsely papillose, refiexed when dry, the segments slender, short, easily broken; spores about 15 ix in diameter, maturing in early spring.
Type locality: Pennsylvania.
Distribution : On the bark of trees ; New England to Florida, west to Illinois and Missouri.