BFNA Title: Macromitrium
5. Macromitrium Bridel, Musc. Rec. suppl. 4 (Mant. Musc.): 132. 1819 * [Name refers to long, large calyptra]
Dale H. Vitt
Plants in dense mats on rocks and trees. Stems creeping with numerous, ascending to erect, simple or forked branches. Branch leaves contorted, spirally twisted, or crisped, rarely erect-appressed when dry, lanceolate, obtuse, sometimes apiculate; margins entire to crenulate; costa percurrent to excurrent; distal laminal cells rounded, bulging, papillose or mammillose; basal laminal cells elongate, thick-walled, tuberculate or smooth. Sexual condition autoicous. Seta 5--12 mm, dextrose. Capsule ovate, becoming narrowly ovate to ovate-oblong when old and dry, plicate below mouth; exothecial cells not differentiated; stomates superficial at base of capsule; peristome single, of 16, rudimentary, pale, delicate, sparsely-striate teeth. Stomates superficial. Calyptrae mitrate, usually covering more than 1/2 the capsule, plicate, lacerate. Spores isomorphic or anisomorphic.
Species ca. 460 (1 in the flora); North, Central, and South America, Asia, Africa, Australia.
Prostrate creeping stems with numerous short, erect branches having terminal sporophyte, a mitrate, plicate calyptra, and a propensity for a chestnut brown color are generic characteristics.
1. Macromitrium richardii Schwägrichen, Spec. Musc. Suppl. 2(2): 70. 173. 1826
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.