William D. Reese
Plants small to robust, tufted or gregarious or cespitose, yellowish-green to blackish. Stem erect or repent, simple or forked; central strand present; rhizoids reddish-brown, inconspicuous; axillary hairs several per axil, with 2--3 short proximal cells and 5--7 long distal cells. Leaves erect to crispate or circinate when dry, ascending when wet, linear to oblong-lanceolate; margins entire to coarsely serrate, thickened distally; costa single, strong; medial cells isodiametric, in longitudinal files, 1-stratose, or 2-stratose in patches, smooth or slightly papillose. Specialized asexual reproduction rare, by axillary uniseriate or branched gemmae. Sexual condition autoicous. Perigonia gemmiform, axillary on short naked stalks. Perichaetia terminal but quickly overtopped by innovations; leaves few, short. Seta single or several from a perichaetium, smooth, straight or flexuous. Capsule erect, exserted, brown, ovoid to cylindric, smooth or wrinkled when dry; stomates scarce, proximal on capsule, phaneropore; annulus revoluble; operculum slenderly rostrate; peristome single, teeth 16, short and broad to long and slender, smooth or densely papillose, mostly irregularly divided into 2--3 slender segments above base. Calyptra mostly mitrate, lobed proximally, often deeply so, naked, smooth or plicate. Spores spherical.
Genera 3, species ca. 80 (2 genera, 6 species in the flora): worldwide, mostly in temperate regions.
The acrocarpous habit, thickened and often serrate leaf margins, smooth or nearly so leaf cells, single peristome, and mitrate, basally lobed, and sometimes plicate calyptra make the Ptychomitriaceae recognizable. The family has been included in the Grimmiaceae by some authors, e.g., S. P. Churchill (1981), E. Lawton (1971), and A. Noguchi (1988), but is recognized as a distinct haplolepideous family by, e.g., H. A. Crum and L. E. Anderson (1981) and D. H. Vitt (1984).
Churchill, S. P. 1981. A phylogenetic analysis, classification and synopsis of the genera of the Grimmiaceae (Musci) in V. A. Funk and D. R. Brooks, eds. Advances in Cladistics, Proc. First Meeting of the Willi Hennig Soc., pp. 127--144. New York Botanical Garden. Crum, H. A. and L. E. Anderson. 1981. Mosses of Eastern North America. New York. Lawton, E. 1971. Moss Flora of the Pacific Northwest. Nichinan. Noguchi, A. Supplemented by Z. Iwatsuki. 19[[add date here]]. Illustrated Moss Flora of Japan, Part 2. Nichinan. Vitt, D. H. 1982. Bryopsida in S. P. Parker, Editor in Chief, Synopsis and Classification of Living Things, Vol. 1, pp. 307--336. New York.