Monographs Details: Hamatocaulis
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 brown and often partly reddish, extensive mats or tufts. Stems creeping to ascending, irregularly to pinnately branched ± in a single plane, the shoot tips typically hooked; in cross-section without a hyalodermis, with small thick-walled cells surrounding larger thinner-walled cells, central strand none; paraphyllia absent; pseudoparaphyllia broadly foliose; axillary hairs with 1(-2) short brown basal cells and 2-6 elongate hyaline distal cells. Stem and branch leaves similar but stem leaves somewhat larger, crowded, abruptly falcate-secund above midleaf from a ± erect base, ovate to broadly ovate, acute to acuminate, usually plicate, not or hardly decurrent; margins irregularly denticulate at extreme apex but otherwise entire, plane; costa single, ending well above midleaf; cells linear, smooth, thin-walled and not porose to firm-walled and porose, especially toward the insertion; alar cells not much differentiated. Asexual propagula none. Dioicous. Perichaetia enlarged, conspicuous; leaves erect, sheathing, ovate-lanceolate, gradually to abruptly acuminate, plicate; margins mostly entire, plane to slightly recurved; costa single, ending above midleaf; cells linear, smooth, firm- to thick-walled, not to strongly porose, becoming shorter, broader, and laxer toward the insertion; alar cells not differentiated. Setae elongate, smooth, reddish, twisted; capsules mostly horizontal, arcuate, asymmetric, cylindric; exothecial cells rounded-quadrate to short-rectangular, firm-walled, not collenchymatous; annulus differentiated, deciduous; operculum conic; exostome teeth yellow-brown, shouldered, strongly bordered, on the front surface papillose-reticulate below, less often papillose-striolate, coarsely papillose above, trabeculate at back; endostome with a high basal membrane, segments keeled, not or narrowly perforate, cilia in groups of (1-)2-5, well developed, nodulose. Spores spherical, finely papillose, medium-sized to large. Calyptrae cucullate, naked, smooth.
Discussion:Discussion. Hamatocaulis is characterized by frequently reddish plants with hooked shoot tips. The stems lack a central strand. The leaves are abruptly curved above the middle. Taxa included in the genus traditionally have been placed in Drepanocladus s.l., but Hamatocaulis differs in the reddish pigmentation, lack of a central strand, axillary hairs with 2-6 elongate distal cells (rather than 1-2), leaves curved only above (rather than falcate throughout), and exostome teeth on the front surface reticulate below (rather than cross-striolate). The genus was monographed for northern Europe when it was described by Hedenãs (1989b).