Monographs Details: Donnellia
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants small to medium-sized, in often lustrous, mostly soft, pale-green to golden, thin mats. Stems creeping, freely but irregularly branched, the branches prostrate or ascending, sometimes curved; in cross-section with small thick-walled cells surrounding large thinner-walled cells, central strand absent; pseudoparaphyllia foliose; axillary hairs with a single short brown basal cell and 1-3 elongate hyaline distal cells. Stem and branch leaves similar, erect to erect-spreading, sometimes homomallous when dry, oblong-lanceolate to lanceolate-ovate, gradually short-acuminate, concave; margins entire to serrulate, plane or narrowly recurved below; costa short and double or absent; cells long-rhomboidal to long-hexagonal, smooth, firm-walled, sometimes becoming shorter and thicker-walled in the acumen; alar cells enlarged, thick-walled, not particularly inflated, colored, in 1-3 rows at the insertion. Asexual propagula rare, gemmiform. Autoicous. Perichaetial leaves erect, oblong-ovate, acuminate; margins often serrulate, plane; costa mostly none; cells long-hexagonal, smooth, firm-walled, becoming laxly rectangular toward the insertion; alar cells not differentiated. Setae short to elongate, smooth, yellow to reddish; capsules erect to suberect, symmetric, straight, cylindric, slightly or not constricted below the mouth when dry; exothecial cells subquadrate to short-rectangular, somewhat collenchymatous; annulus differentiated; operculum obliquely long-rostrate; peristome double, exostome teeth bone-white when dry, ± hyaline when moist, closely placed, on the front surface with a straight median line, not furrowed, smooth or finely roughened but with prominent, often densely papillose crosswalls, slightly trabeculate at back; endostome with basal membrane very low or absent, segments finely papillose, linear, ± keeled, not perforate, almost as long as the teeth, often broken off in deoperculate capsules, cilia none. Spores spherical, papillose. Calyptrae cucullate, naked, smooth.
Discussion:Donnellia Austin, Bull. Torrey Bot. Club 7: 5. 1880.
Meiotheciopsis Broth, in Engl. & Prantl, Nat. Pflanzenfam. 1(3): 1105. 1908.
Meiothecium sect. Pterogonidiopsis Broth, in Engl. & Prantl, Nat. Pflanzenfam. 1(3): 1101. 1908.
Discussion. I (Buck, 1982, as Meiotheciopsis) expanded Donnellia to include the species previously included in Meiothecium sect. Pterogonidiopsis. All the species in the section have peristomes almost identical to Meiotheciopsis s.str., including the reduced endostome. However, the name Donnellia was found to be the correct name for the genus (Buck, 1988c). I (Buck, 1994b) described and mapped the American species. The genus is defined primarily on the basis of the peristome. It is bone-white when dry, and the exostome teeth are closely spaced and essentially smooth except for the prominent plate boundaries. The endostome is reduced and often difficult to demonstrate unless mature operculate capsules are dissected. In recently dehisced capsules, the endostome may be seen with a dissecting microscope on dry capsules, because the segments stick straight up between the teeth. The leaves tend to have longer cells than typical for Meiothecium.