Monographs Details: Pterobryon
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants robust, in mostly dark-green, dense, epiphytic colonies. Primary stems creeping, filiform, with small, reduced leaves, turning ca. 90° and becoming the upright secondary stem (stipe), the creeping stem continuing by a bud from near the base of the stipe, stipes frondose and regularly pinnately branched, erect; in cross-section with small thick-walled cells surrounding larger thinner-walled cells, the central strand none; paraphyllia none; pseudoparaphyllia filamentous, numerous; axillary hairs with 1-2 short to rectangular brown basal cells and 2-3 elongate hyaline to brown distal cells. Stipe leaves differentiated from branch leaves, erect-appressed from a clasping base, oblong-lanceolate, decurrent; margins subentire, plane; costa single, ending below midleaf; cells linear, smooth, thick-walled, porose; alar cells scarcely differentiated. Branch leaves spreading, not conspicuously ranked, lanceolate, acuminate, plicate, short-decurrent; margins serrate above, subentire below, plane; costa single, ending above midleaf, projecting as a small spine; cells linear, smooth, thick-walled, porose; alar cells scarcely differentiated. Asexual propagula often clustered in leaf axils, uniseriate. Dioicous. Perichaetia large, conspicuous; leaves oblong-lanceolate, long-acuminate; margins serrulate above, entire below, plane; costa single, ending near midleaf; cells linear, smooth, thick-walled, porose. Setae short, smooth; capsules immersed, cylindric, erect and symmetric; exothecial cells hexagonal, firm-walled; annulus differentiated; operculum obliquely conic-rostrate; peristome double, inserted below the mouth, prostome well developed, exostome teeth not bordered or shouldered, ± unornamented, not trabeculate at back; endostome rudimentary. Spores spherical to ovoid, large, almost smooth. Calyptrae mitrate, naked, smooth.
Discussion:Pterobryon Hornsch. in Mart., Fl. Bras. 1(2); 50. 1840; Pilotrichum sect. Pterobryon (Hornsch.) Müll. Hal., Syn. Musc. Frond. 2: 179. 1851, “Pterobryum."
Discussion. Pterobryon is characterized by relatively robust, frondose plants with plicate leaves and immersed capsules. In our flora it is very similar to Pireella, especially species like Pireella angustifolia. Pterobryon may be consistently separated from Pireella by the larger stature and plicate leaves. However, the Asian species of Pterobryon are smaller, less regularly frondose, and plicate only when dry. The genus has only about 4-6 species, with two in the New World.