Monographs Details: Micromitrium
Authority: Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part One: Sphagnales to Bryales. Mem. New York Bot. Gard. 69 (1)
Description:Species Description - Plants minute, scattered to gregarious, usually arising from a sparse protonema. Leaves generally shriveled and somewhat contorted when dry, lanceolate to oblong- or ovate-lanceolate, broadly to narrowly acuminate, entire to bluntly serrulate above the middle, ecostate or nearly so (or rarely costate); cells lax, thin-walled, and smooth, oblong-hexagonal to rhomboidal above. Capsules sessile, globose, not apiculate (or rarely minutely so), dehiscing near the middle along a line of weakness (or, less often, rupturing irregularly); exothecial cells irregularly hexagonal, usually large and delicate. Spores medium-sized to large, reniform, papillose. Calyptrae minute and delicate (scarcely more than the remains of the archegonium), persistent.
This genus of minute ephemerals differs from Ephemerum in having a sparse protonema, leaves shriveled and contorted when dry with no costa and smooth cells, capsules not or dehiscent near the middle, and calyptrae persistent and consisting of little more than the remains of a small archegonium.