Monographs Details: Orthostichella
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants relatively slender to medium-sized, but often in exceedingly long, pendent, ± lustrous, ± stiff, pale-green to golden, dense colonies. Stems usually very elongate, pendent, subpinnate to irregularly branched, the branches typically becoming secondarily branched; in cross-section with small thick-walled cells surrounding larger firm-walled cells, central strand none; paraphyllia absent; pseudoparaphyllia broadly foliose; axillary hairs with 1-2 short brown basal cells and 1-3(-5) elongate hyaline distal cells. Stem and branch leaves scarcely differentiated except somewhat in size, conspicuously seriately ranked, especially when moist, erect to spreading, typically oblong-obovate, sometimes panduriform, cuspidate to short-acuminate, deeply concave at least above, usually rounded to the insertion and thus ± cordate but not at all auriculate, not decurrent; margins serrulate above or almost throughout, usually broadly incurved above; costa none or single and very short, ending below 1/4 the leaf length, sometimes short and double; cells long-hexagonal, subflexuose, smooth, firm-walled, not or scarcely porose; alar ceils gradually differentiated, few, subquadrate, mostly yellow. Asexual propagula none but leaves sometimes caducous, leaving naked branches. Dioicous. Perichaetia conspicuous, on branches, with conspicuous paraphyses and vaginular hairs almost as long as to longer than the leaves; leaves differentiated, erect with spreading apices, oblong-lanceolate, gradually acuminate; margins subentire to serrulate, plane; costa none; cells as in vegetative leaves; alar cells not differentiated. Setae short, vaguely roughened to smooth, yellowish, ca. 3-5 mm long; capsules exserted, erect, symmetric, cylindric; exothecial cells subquadrate to short-rectangular, firm-walled, becoming smaller and oblate toward the mouth; annulus differentiated in a few rows of small oblate thick-walled cells; operculum obliquely rostrate; exostome teeth linear-triangular, pale, not or scarcely shouldered, not or narrowly bordered, on the front surface papillose throughout or sometimes with basalmost plants obscurely cross-striolate, not or scarcely trabeculate at back; endostome with a low basal membrane, segments ± papillose, keeled, narrowly perforate, cilia rudimentary or none. Spores spherical, papillose. Calyptrae cucullate, naked to sparsely erect-hairy, smooth to roughened.
Discussion:Orthostichella Müll. Hal., Bull. Herb. Boissier 5: 204. 1897.
Neckera sect. Pseudopilotrichum Müll. Hal., Syn. Muse. Frond. 2: 123. 1850; Pseudopilotrichum (Müll. Hal.) W. R. Buck & B. H. Allen in W. R. Buck, J. Hattori Bot. Lab. 75: 69. 1994.
Neckera sect. Pseudopilotrichum subsect. Ortho stichella Müll. Hal., Syn. Muse. Frond. 2: 123. 1850.
Discussion. Orthostichella is used here as a segregate of Pilotrichella for the assemblage of small-statured species that had been accommodated in that genus. The group is differentiated from Pilotrichella by nonauriculate leaf bases, weakly differentiated alar regions, short setae, oblique opercula, ± papillose exostome teeth, and smaller spores, as well as the smaller stature. Orthostichella is differentiated from Squamidium by the lack of a costa and the poorly developed alar regions, as well as the cucullate calyptrae and lack of a central strand in the stems. There may be some confusion with the distantly related Hildebrandtiella, but there the prominent filamentous pseudoparaphyllia in addition to the very different sporophytes will aid in recognition.
Midler’s use of the name Orthostichella as a subsection (1850) and as a genus (1897b) is probably more than coincidental. Both taxa refer to the same taxonomic concept, i.e., that presented here. However, Midler (1897b) made no reference to his previous usage.
Orthostichella is distributed widely in tropical America and Africa. Many epithets have been described but the number of species is surely many fewer. In the West Indies we have one widespread and one endemic species.