Monographs Details: Drepanocladus
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants medium-sized to robust, in stiff to soft, ± lustrous, green to golden, never reddish, extensive mats or tufts. Stems creeping to ascending, irregularly to pinnately branched ± in a single plane; in cross-section with or without a hyalodermis, with small thick-walled cells surrounding larger thinner-walled cells, central strand present, of small thin-walled cells; paraphyllia absent; pseudopa-raphyllia foliose; axillary hairs with 1-2 short brown basal cells and 1-2(-3) elongate hyaline distal cells. Stem and branch leaves similar but stem leaves somewhat larger and more acuminate, crowded, typically falcate-secund throughout, often strongly so, lanceolate to ovate-lanceolate, acuminate, ± concave, not plicate, not or hardly decurrent; margins entire, plane to erect; costa single, ending from midleaf to excurrent; cells linear, occasionally shorter, smooth, thin-walled and not porose to thick-walled and porose, especially toward the insertion; alar cells differentiated, often in auricules, sometimes in concave areas extending from margin almost to costa, usually hyaline, enlarged, inflated, thin-walled, sometimes thick-walled and colored. Asexual propagula none. Dioicous. Perichaetia enlarged, conspicuous; leaves erect, sheathing, oblong-lanceolate, acuminate, often plicate; margins mostly entire, plane to erect; costa single, ending at midleaf or above; cells linear, smooth, firm- to thick-walled, not to strongly porose, becoming shorter, broader, and laxer toward the insertion; alar cells not or slightly differentiated. Setae elongate, smooth, yellowish to reddish, twisted; capsules inclined to horizontal, arcuate, asymmetric, cylindric to ovoid, with a long neck, often striate, somewhat constricted below the mouth when dry; exothecial cells rounded-quadrate to short-rectangular, firm-walled, not collenchymatous; annulus differentiated, deciduous; operculum apiculate to short-rostrate from a conic base; exostome teeth yellow-brown, shouldered, strongly bordered, on the front surface cross-striolate below, sometimes with overlying papillae, coarsely papillose above, trabeculate at back; endostome with a high basal membrane, segments keeled, not or narrowly perforate, cilia in groups of (1-)2-4, nodulose. Spores spherical, finely papillose, large. Calyptrae cucullate, naked, smooth.
Discussion:Drepanocladus (Müll. Hal.) G. Roth, Hedwigia 38(Beibl.): 6. 1899; Hypnum sect. Mallacodium Müll. Hal. subsect. Drepanocladus Müll. Hal., Syn. Muse. Frond. 2: 321. 1851.
Hypnum sect. Harpidium Sull. in A. Gray, Manual, ed. 2, 673. 1856; Hypnum subgen. Harpidium (Sull.) A. A. Fisch. Waldh., Bull. Soc. Imp. Naturalistes Moscou 37(3): 38. 1864; Harpidium (Sull.) Spruce, Cat. Musc. 21. 1867, hom, illeg., non Körb., Syst. Lich. Germ. 157. 1855 [Lichenaceae]; Amblystegium sect. Harpidium (Sull.) Mitt, in Godm., Nat. Hist. Azores 312. 1870.
Discussion. Drepanocladus is generally recognized by its falcate-secund leaves with a single costa. The plants characteristically grow in moist to aquatic habitats. The genus has been subjected to elaborate dissection in recent years (e.g., Tuomikoski et al., 1973), probably justifiably so. Crum and Anderson (1981: 960, 961) discussed the generic segregates in a knowledgeable way but failed to follow them. Representation of Drepanocladus s.l. in the West Indies is minimal and therefore an evaluation of the overall situation would be presumptuous and beyond the realm of my experience. Therefore, I have followed recent work by Hedenäs (e.g., 1993, 1998).
From a North American perspective it appears as if almost every well-known species in Drepanocladus sd. has been moved if not to an unfamiliar genus then at least to an unfamiliar circumscription of a well-known generic name. However, a large suite of characters ranging from the obvious (e.g., pigmentation) to the obscure (e.g., vestiture of the vaginula) seem to define the genera. Of interest to field-oriented bryologists is that the phytogeny also coincides with ecological parameters of the habitats of the taxa. The problem associated with generic definition was first sorted out by Loeske (1907).
The North American species of Drepanocladus sd. were monographed by Wynne (1944). It remains a useful reference.