Isopterygiopsis Z. Iwatsuki, J. Hattori Bot. Lab. 33: 379. 1970.
[Greek iso, equal, pteron, winged, and opsis, appearance]
Robert R. Ireland
Plants small, sometimes complanate, in thin to dense, light- to yellowish-green glossy mats. Stems 1--2 cm, creeping, simple or sparingly and irregularly branched, epidermal layer of stem cells small to large, with thin exterior walls and thick interior ones, central strand sometimes present; rhizoids papillose, in clusters in leaf axils; axillary hairs hyaline, with one short-rectangular basal cell and two elongate apical cells; paraphyllia and pseudoparaphyllia lacking. Leaves of stems and branches similar, somewhat rigid, crowded and imbricate, erect-spreading, occasionally secund, sometimes complanate and pectinate, smooth, flat or somewhat concave, symmetric, nondecurrent, lanceolate or ovate- to oblong-lanceolate, long-acuminate to abruptly acuminate; margins plane to erect, entire or minutely serrulate; costa lacking or short and double; cells often flexuose, firm-walled, linear-fusiform, smooth or minutely prorulose at distal and proximal ends on dorsal leaf surface, with walls not pitted; alar cells not differentiated or sometimes with 1--3 quadrate to short-rectangular cells on margins. Specialized asexual reproduction sometimes present as brood bodies in clusters in leaf axils on stems and branches, cylindric or fusiform, 28--96 ´ 5--14 µm, composed of 2--6 smooth cells. Sexual condition autoicous or dioicous; perigonia and perichaetia clumped at base of stems and branches, bracts small, lanceolate to ovate, acuminate to abruptly filiform-acuminate, margins plane. Seta solitary, red to reddish brown, 0.6--2 cm, twisted, straight to somewhat curved, smooth. Capsule erect to cernuous, straight to subarcuate, yellow to light- or orange-brown, oblong to ovoid, smooth, contracted below mouth and wrinkled at neck when dry; annulus of 2--3 rows of cells, deciduous; operculum conic to obliquely rostrate, shorter than urn; stomata sparse, present in the neck, superficial; peristome double, exostome teeth cross-striolate proximally, papillose distally, bordered, trabeculate on interior surface; endostome with a high to low basal membrane, keeled segments, cilia shorter than segments, in groups of 1--3, sometimes absent. Calyptra cucullate, smooth, naked. Spores spherical to ovoid, smooth or minutely papillose.
Species 3 (3 in the flora): North America, South America, Europe, Asia, Africa, Pacific Islands (New Zealand).
Plants of this genus occur in terrestrial habitats in boreal and temperate woods, as well as in the Arctic.
Ireland, R. R. 1969. A taxonomic revision of the genus Plagiothecium for North America, north of Mexico. National Museums of Canada, Nat. Mus. Nat. Sciences, Publs. in Botany 1: 1--118. Iwatsuki, Z. 1970. A revision of Plagiothecium and its related genera from Japan and her adjacent areas, I. J. Hattori Bot. Lab. 33: 331-- 380. Iwatsuki, Z. 1987. Notes on Isopterygium Mitt. (Plagiotheciaceae). J. Hattori Bot. Lab. 63: 445--451. Vitt, D. H. 1990. The distribution of North American bryophytes Isopterygiopsis muelleriana (Schimp.) Iwat. Evansia 7: 13--14.
Flowers, S. 1973. Mosses: Utah and the West. Plagiothecium, pp. 520--524. Provo.
Tuomikoski, R. 1939. Materialien zu einer Laubmoosflora des Kuusamo-Gebietes. Ann. Bot. Soc. Fenn. Vanamo 12(4): 1--124.