4. Micromitrium wrightii (Müller Hal.) Crosby, Bryologist. 71: 116. 1968.
Ephemerum wrightii Müller Hal., Linnaea 43: 351. 1882; Nanomitrium wrightii (Müller Hal.) V. S. Bryan & L. E. Anderson
Plants scattered in abundant pro-tonemata, green. Stems virtually absent. Leaves erect, linear-lanceolate, rarely with narrow, toothed shoulders, gradually and slenderly acuminate, 1-2 × 0.15-0.26 mm, margins plane, entire or with short single or double teeth distally. Sexual condition synoicous or dioicous. Capsule cleistocarpous or rarely dehiscing by a ring of differentiated cells distal to the equator, yellow- to orange-brown, globose or slightly flattened, slightly apiculate; exothecial cells in 2 layers, stomates numerous and confined to proximal half. Spores fewer than 100, various shapes, proximal face not concave, 50-84 × 40-66 µm, red-brown or dark brown.
Capsules mature year around. Soil in shaded ravines, drying mud, clay in dry sloughs; low elevations (0-100 m); La., Tex.; West Indies (Cuba).
Although the leaves of Micromitrium wrightii are most accurately described as ecostate, the largest leaves may have suggestions of a costa. Some have merely thick-walled cells in the median part of the leaf, and others may have ± 3 median, undifferentiated cells in a double layer.
Micromitrium wrightii is known from five or fewer localities.