Monographs Details: Pylaisiadelpha
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants slender to moderately robust, in often lustrous, green to golden mats. Stems creeping, freely branched, sometimes regularly so, the branches prostrate to erect, densely foliate; in cross-section with the outermost layer with the outer walls ± thin, otherwise with small thick-walled cells surrounding larger thinner-walled cells, central strand absent; pseudoparaphyllia filamentous to narrowly foliose; axillary hairs with a single rectangular brown basal cell and 2-4 elongate hyaline distal cells. Stem and branch leaves similar, crowded, erect-spreading to spreading, homomallous to falcate-secund, obscurely to distinctly complanate, lanceolate to ovate, narrowly acuminate, often concave; margins serrulate above, subentire below, often recurved below; costa short and double or absent; cells long-rhomboidal to linear, smooth, often firm-walled, mostly not or only weakly porose; alar cells enlarged and ± inflated, colored, thick-walled, oblong. Asexual propagula sometimes clustered in leaf axils, filamentous. Mostly dioicous. Perichaetial leaves erect, lanceolate to oblong-ovate, acuminate; margins toothed above, usually entire below, plane; costa mostly none; cells linear, smooth, often thick-walled and porose, becoming shorter toward the insertion; alar cells not differentiated. Setae elongate, smooth, usually reddish; capsules usually inclined, occasionally erect, usually ± asymmetric, oblong-ovoid to cylindric; exothecial cells rectangular, not collenchymatous; annulus differentiated in 1-2 rows or absent; operculum short- to long-rostrate; peristome double, exostome teeth narrowly triangular, shouldered, bordered, on the front surface with a zig-zag median line, cross-striolate below, coarsely papillose above, trabeculate at back; endostome with a ± high basal membrane, segments finely papillose, mostly broad, keeled, perforate, almost as long as the teeth, cilia in groups of 1-2 or rudimentary to absent. Spores spherical, smooth or finely papillose. Calyptrae cucullate, naked, smooth.
Discussion:Pylaisiadelpha Cardot, Rev. Bryol. 39: 57. 1912.
Brotherella Loeske, Stud. Morph. Laubm. 175. 1910, nom. nud., Loeske ex M. Fleisch., Nova Guinea 12(1, Bot., 2): 119. 1914.
Discussion. Pylaisiadelpha has long been better known as Brotherella. However, the type of Pylaisiadelpha, P rhaphidostegioides, is a synonym of Brotherella tenuirostris. The genus is characterized by usually falcate-secund leaves with serrate to serrulate margins and somewhat enlarged and colored alar cells. The genus is particularly diverse in the Asian tropics and those species, usually growing on small branches, scarcely resemble the few North Temperate species.
Some (Ando et al., 1989) have argued for recognition of both Pylaisiadelpha and Brotherella, placing the former in the Hypnaceae and the latter in the Sematophyllaceae. Even if one could recognize both genera—and I remain unconvinced of the value of such segregation (primarily to salvage a well-known name)—I would currently place both in the Sematophyllaceae.