Monographs Details: Heterophyllium
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants medium-sized, in somewhat lustrous, ± soft, dark- to yellow-green to golden, extensive mats. Stems creeping, subpinnately branched; in cross-section with small thick-walled cells surrounding large thinner-walled cells, central strand absent; pseudoparaphyllia narrowly foliose; axillary hairs with 2 rectangular brown basal cells and 3 elongate hyaline distal cells. Stem and branch leaves slightly differentiated, branch leaves erect to erect-spreading, lanceolate to ovate, long-acuminate, concave; margins serrate above, plane to narrowly reflexed; costa short and double or absent; cells linear, smooth, thick-walled; alar cells subquadrate, thick-walled, yellowish, in well-differentiated excavate groups. Asexual propagula none. Autoicous or rarely dioicous. Perichaetia large; leaves oblong-lanceolate, long-acuminate; margins coarsely serrate, plane; costa mostly none; cells linear, smooth, thick-walled, porose; alar cells not differentiated. Setae elongate, smooth, reddish; capsules suberect to inclined, ± asymmetric, cylindric; exothecial cells short-rectangular, thick-walled, not collenchymatous; annulus somewhat differentiated; operculum short- to long-conic; peristome double, exostome teeth narrowly triangular, shouldered, bordered, on the front surface with a zig-zag median line, not furrowed, cross-striolate below, coarsely papillose above, trabeculate at back; endostome hyaline or yellowish, with a high basal membrane, segments broad, keeled, not perforate, almost as long as the teeth, cilia well developed. Spores spherical, smooth or almost so. Calyptrae cucullate, naked, smooth.
Discussion:Heterophyllium (Schimp.) Müll. Hal. ex Kindb., Canad. Rec. Sci. 6: 72. 1894, “Heterophyllum," non Heterophyllum Bojer ex Hook., Bot. Misc. 1: 291. 1830, nom. nud. in syn. [= Byttneria, Byttneriaceae], nec Heterophyllium Hieron. ex Bömer, Fl. Deut. Volk 110. 1912 [= Diplostachyum P. Beauv., = Selaginella P. Beauv., Selaginellaceae]; Hypnum subgen. Heterophyllium Schimp., Syn. Musc. Eur. 629. 1860; Stereodon subgen. Heterophyllium (Schimp.) Broth, in Engl. & Prantl, Nat. Pflanzenfam. 1(3): 1072. 1908.
Discussion. The nomenclatural problems surrounding the generic name and its sole species have been explored in detail by Robinson and Reed (1966). The genus is readily recognized by long-acuminate leaves with gradually tapered, strongly serrate acumina and well-differentiated alar cells in excavate groups.