Monographs Details: Chryso-hypnum
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants mostly small, sometimes medium-sized, in soft, dark-green to golden, often extensive, dense mats. Stems creeping, prostrate, with rhizoids all along the underside, freely and irregularly to regularly pinnately branched, the branches mostly simple, short, blunt, densely foliate; in cross-section without a hyalodermis, with small thick-walled cells surrounding larger thinner-walled cells, central strand small or absent; pseudoparaphyllia foliose; axillary hairs with 1-3 short brown basal cells and 1-2 ± elongate hyaline brown distal cells. Stem and branch leaves similar, erect- to wide-spreading, soft, mostly ovate, ± abruptly short- to long-acuminate, sometimes concave, seldom plicate, not or scarcely decurrent; margins serrulate, often throughout, plane to erect or recurved; costa short and double; cells linear, prorulose at upper and sometimes lower ends at back, rarely smooth, often firm-walled, becoming shorter and broader toward the insertion; alar cells few in extreme angles, quadrate to short-rectangular. Asexual propagula none. Mostly autoicous, rarely dioicous. Perichaetial leaves erect, lanceolate, gradually long-acuminate; margins sparsely serrulate, plane; costa short and double or none; cells linear to linear-flexuose, smooth or low-prorulose, thin- to firm-walled, becoming shorter and broader toward the insertion; alar cells sometimes differentiated in extreme angles. Setae elongate, smooth, reddish, twisted; capsules horizontal to pendent, ± arcuate, somewhat asymmetric, mostly ovoid to short-cylindric, usually with a differentiated neck, often constricted below the mouth when dry; exothecial cells quadrate to short-rectangular, the vertical walls firm, those of the crosswalls thin and wavy; annulus differentiated; operculum conic, mostly apiculate; peristome double, exostome teeth shouldered, bordered, on the front surface cross-striolate below, coarsely papillose above, trabeculate at back; endostome with a high basal membrane, segments keeled, perforate, ca. as long as the teeth, cilia in groups of 1-3. Spores spherical, finely papillose. Calyptrae cucullate, mostly sparsely to densely hairy, rarely naked, smooth.
Discussion:Chryso-hypnum (Hampe) Hampe, Bot. Zeitung (Berlin) 28: 35. 1870, “Chryso-Hypnumnon Chrysohypnum G. Roth, Hedwigia 38(Beibl. 1): 7. 1899, horn, illeg. [=Campylium (Sull.) Mitt.]; Hypnum subgen. Chryso-hypnum Hampe, Flora 50: 76. 1867; Hypnum subgen. Chrysohypnum Hampe, Bot. Zeitung (Berlin) 10: 71. 1852, nom. nud.
Microthamnium sect. Pseudo-microthamnium Broth, in Engl. & Prantl, Nat. Pflanzenfam. 1(3): 1049. 1908; Mitteno-thamnium sect. Pseudo-microthamnium (Broth.) Wijk & Margad., Taxon 11: 222. 1962. Lectotype (chosen here): Microthamnium diminutivum (Hampe) A. Jaeger.
Stereohypnum sect. Stereohypnella M. Fleisch., Hedwigia 47: 274. 1908. Lectotype (chosen here): Stereohypnum thelistegum (Müll. Hal.) M. Fleisch.
Discussion. Chryso-hypnum is here defined by prostrate, soft plants with ovate leaves and cells that are prorulose at one or both ends. Other differences from Mittenothamnium, from which it is segregated (Buck, 1984), are the nonstipitate plants, the shorter capsules with apiculate opercula, and the usually hairy calyptrae. Fleischer 's (1908) treatment of some of the species of this genus is worthy of consultation. Subsequent work by Nishimura and Ando