Branches to 1 cm. Branch leaves strongly crisped and inrolled when dry, lanceolate to ligulate-lanceolate, 0.7--1.8 mm, sharply acute, obtuse, or obtusely apiculate; distal laminal cells 7--11 µm wide, irregularly hexagonal to rounded-elliptic, bulging at mid leaf, grading to papillose-bulging at tip; basal laminal cells rectangular to elongate-linear. Perichaetial leaves similar to the cauline. Calyptra mitrate, naked, or with few hairs covering entire capsule. Spores 22--32 µm, densely papillose.

Capsules mature spring. Branches and trunks of trees; low elevations; Fla., La., Miss.; Mexico; West Indies; Central America; South America.

The only species of Macromitrium occurring in the United States, this species is distinguished from other mosses with creeping stems and erect branches by the non-rugose, inrolled leaves, and the uniformly elongate basal leaf cells. The papillose-bulging distal leaf cells and autoicous sexual condition distinguish this species from other species of Macromitrium in the tropical portions of its range.