Monographs Details: Lepidopilum
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants mostly medium-sized, sometimes smaller or robust, in mostly lustrous, bright-green or less often golden or reddish, dense or lax mats or tufts. Stems creeping, often short, often with eroded leaves, with erect primary branches, mostly complanate-foliate; in cross-section with a unistratose hyalodermis of large cells over medium-sized thick-walled cells surrounding large thin-walled cells, central strand none; rhizoids tufted on stems and very base of primary branches, lightly roughened; pseudoparaphyllia mostly foliose; axillary hairs 2-celled, with a short brown basal cell and an elongate hyaline distal cell. Leaves sometimes contorted dry or moist, laxly or densely foliate, lateral and dorsal leaves often differentiated in size, shape, and symmetry, lateral leaves mostly wide-spreading, oblong-lanceolate to broadly ovate, gradually to abruptly acute to acuminate, rarely obtuse, asymmetric, sometimes very strongly so, dorsal leaves erect to erect-spreading, mostly oblong-ovate, mostly ± abruptly short-acuminate, ± symmetric; margins sometimes bordered by elongate, narrow cells, usually indistinct at leaf base, entire to serrate, plane or narrowly recurved; costa double, often slender, ± divergent throughout, mostly ending at midleaf or below, not projecting at apex; cells mostly long-hexagonal, rarely hexagonal, the apical ones sometimes shorter than those at midleaf, smooth, thin- or firm-walled, becoming shorter and often colored in 1-3 rows across the insertion; alar cells not differentiated. Asexual propagula common in leaf axils, uniseriate, mostly chlorophyllose. Autoicous, synoicous, or dioicous. Perichaetia small, inconspicuous, in leaf axils of primary branches; leaves few, erect, pale, mostly narrowly triangular, gradually or abruptly acuminate; margins not or narrowly bordered, entire throughout or serrulate above, typically plane; costa none; cells mostly long-hexagonal. Setae often short, sometimes elongate, typically papillose throughout, rarely only above or smooth throughout, reddish; capsules erect, symmetric, cylindric; exothecial cells subquadrate to rectangular, often firm-walled, not at all or conspicuously collenchymatous; annulus of a single row of quadrate cells, usually falling with the operculum; operculum high-conic to conic-rostrate; columella usually extending to near mouth, broadly cylindric; peristome double, attached at mouth, exostome teeth narrowly triangular, typically recurved when dry, sometimes erect, strongly bordered, papillose throughout, on the front surface usually pale, not furrowed, on back surface mostly reddish, somewhat trabeculate; endostome yellowish, papillose throughout, with a low basal membrane, segments erect, not or scarcely keeled, mostly not perforate, ca. as long as the teeth, cilia mostly none, rarely rudimentary. Spores spherical, ± smooth to finely papillose. Calyptrae mitrate, covering the operculum and upper 1/3-1/2 of urn, lobed at base, often plicate, hairy with multiseriate ramenta and sometimes uniseriate hairs, smooth or roughened at apex.
Discussion:Lepidopilum (Brid.) Brid., Bryol. Univ. 2: 267. 1827, nom. conserve, Pilotrichum sect. Lepidopilum Brid., Muscol. Recent. Suppl. 4: 141. 1819; Hookeria sect. Lepidopilum (Brid.) Müll. Hal., Syn. Musc. Frond. 2: 192. 1851.
Lepidopilum sect. Hemiragiella Besch., J. Bot. (Morot) 8: 63. 1894.
Discussion. Lepidopilum is characterized by few consistent gametophytic features except a relatively short costa. Plants are often complanate-foliate but not always. Leaves vary from oblong-lanceolate to broadly ovate; they are sometimes, but not always, bordered; the leaf cells vary from ± isodiametric to long-hexagonal. Sporophytically, the setae are often (but not always) short, usually less than 1 cm, and are usually papillose to hispid throughout. The capsules are erect and cylindric, with or without collenchymatous exothecial cells. The exostome, usually recurved when dry, is broadly bordered and densely papillose throughout. The endostome has a low basal membrane and erect, scarcely keeled segments. The calyptra is typically ornamented with multiseriate ramenta, sometimes with uniseriate hairs as well.
Although placed by some authors in the Daltoniaceae because of the papillose exostome teeth, the relationships of Lepidopilum are surely with the double-costate genera. Even though the teeth are papillose, they are very different from those of Daltonia, which are only narrowly bordered. Lepidopilum, as well as Lepidopilidium and Crossomitrium, seem very near Stenodictyon and especially Actinodontium. Because of stem anatomy, axillary hair structure, costal morphology, and areolation, a relationship with those hookeriaceous genera that otherwise differ in having cross-striolate exostome teeth, strong double costae, and enlarged stem cortical cells, seems most likely.
Lepidopilum is gametophytically inseparable from Lepidopilidium. They differ, consistently, only in peristome morphology. In Lepidopilum the exostome teeth are densely papillose throughout and not furrowed on the front surface; Lepidopilidium has furrowed, cross-striolate exostome teeth. The endostome in Lepidopilidium is like many Hookeriales, with baffle-like crosswalls on the segments, thus resembling a longitudinal section of a bamboo culm.
Lepidopilum was monographed by Churchill (1988) in an unpublished doctoral dissertation. Most of his conclusions are followed here, even though my manuscript was finished prior to the dissertation.