Isodrepanium

• Authority

  Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.

• Family

  Neckeraceae

• Scientific Name

  Isodrepanium

• Description

  Genus Description - Plants medium-sized to somewhat robust, in very lustrous, pale-green to golden, often dense, untidy mats or pendulous. Primary stems creeping, occasionally pendent, irregularly 1-2-pinnate, secondary stems not differentiated, branches arising laterally, complanate-foliate; in cross-section with small thick-walled cells surrounding larger thinner-walled cells, central strand none; paraphyllia none; pseudoparaphyllia foliose; axillary hairs with (1-)2(-3) short brown basal cells and (2-)3-5 elongate hyaline distal cells. Leaves strongly complanate, spreading to wide-spreading, ± falcate-cultriform, strongly asymmetric, not decurrent; margins serrulate above, subentire below, indexed on one side below; costa short and double; cells elongate, smooth, firm-walled, porose; alar cells not differentiated. Asexual propagula none. Dioicous. Perichaetial leaves strongly differentiated, convolute, oblong-subulate; margins serrulate above, subentire below, plane; costa obscurely single; cells linear, smooth, thick-walled, porose. Setae very long, smooth; capsules suberect to horizontal, broadly short-cylindric; exothecial cells short-rectangular, thick-walled, not collenchymatous, stomata phaneropore; annulus probably not differentiated; operculum not seen; peristome double, inserted below the mouth, exostome teeth on the front surface densely cross-striolate below, papillose above, trabeculate at back; endostome with a high basal membrane, segments keeled, perforate, ca. as long as the teeth, cilia ?present. Spores spherical, finely papillose. Calyptrae not seen.

• Discussion

  Isodrepanium (Mitt.) E. Britton in E. Britton & R. S. Williams, Torreya 14: 27. 1914; Lepidopilum sect. Isodrepanium Mitt., J. Linn. Soc., Bot. 12: 366. 1869; Homalia sect. Isodrepanium (Mitt.) Müll. Hal., Hedwigia 37: 266. 1898. Discussion. Isodrepanium is a monospecific genus restricted to the New World tropics. It is characterized by strongly asymmetric, complanate leaves. The laminal cells are distinctly porose and the costa is short and double. The setae are very long and bear a relatively short, small capsule. The peristome is typically hypnoid. The genus was treated by Welch (1976: 76, 77) as belonging to the Hookeriales. However, Crum and Steere (1957: 529) moved it to the Neckeraceae on the basis of information from K. A. Wagner on phyllotaxy. Unfortunately, Wagner apparently never published his data and it is not in his dissertation (Wagner, 1951). Except for its cultriform leaf shape, Isodrepanium seems closely related to Homalia, from which it was originally segregated. Isodrepanium might be confused with some species of Lepidopilum, but the distinctive areolation of Isodrepanium, as well as its sporophytic features, will keep it apart. Although helpful in assessing relationships, sporophyte characters are of little practical value in identification due to their great rarity.