Monographs Details: Diploneuron
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, in dull or slightly lustrous, dark-green to golden, thin mats. Stems creeping, brittle, intricately and irregularly branched, the branches not differentiated, evenly foliate; in cross-section without a hyalodermis, with medium-sized thick-walled cells surrounding larger firm-walled cells, central strand none; rhizoids tufted on lower surfaces of stems, roughened; pseudoparaphyllia foliose; axillary hairs 2-celled, with a short brown basal cell and an elongate hyaline distal cell. Leaves ± contorted when dry, densely foliate, isophyllous, lanceolate to oblong-lanceolate, acuminate, symmetric, rounded to the insertion; margins not bordered, entire to crenulate, the extreme apex sometimes serrulate, plane; costa double, strong, broad, diverging to leaf margin and then running along it forming thickened border, fusing above and filling the subula; cells oval to irregularly angled, short, smooth, thick-walled, porose, more strongly so below, slightly broader across the insertion, not or rarely colored; alar cells not differentiated. Asexual propagula unknown. Apparently dioicous. Perichaetia relatively large, conspicuous, usually clustered on stems; leaves many, spreading, oblong-ovate, ± abruptly broad-acuminate; margins not bordered, serrulate above, entire below, plane; costa double, broad, ± parallel or slightly diverging below, then converging and running parallel to margin, forming thickened border, fusing above and filling the acumen; cells long, smooth, firm-walled, porose, becoming longer, broader, thinner-walled and nonporose toward insertion. Setae elongate, smooth through-out or slightly roughened at apex, reddish, twisted; capsules inclined to horizontal, cylindric, symmetric; exothecial cells short-rectangular, thin-walled at surface, with collenchymatous thickenings below the surface; annulus not differentiated; operculum conic-rostrate; columella broadly cylindric, almost as long as the urn; peristome double, attached at the mouth, exostome teeth reddish, narrowly triangular, narrowly bordered, not shouldered, on the front surface narrowly furrowed, the plates cross-striolate with overlying papillae below, papillose above, scarcely trabeculate at back; endostome yellowish, with a relatively high basal membrane, segments keeled, perforate, with baffle-like crosswalls, cilia none. Spores spherical, finely papillose. Calyptrae mitrate. lobed at base, sparsely hairy, smooth.
Discussion:Discussion. Diploneuron is unlikely to be confused with any other moss. The leaves have a broad double costa that diverges until it reaches the margin and then runs up it forming a thickened border that unites above to form a long, thick subula. The perichaetia are large and leafy and the setae are long, with typically horizontal capsules. The exostome is furrowed. The plants are apparently dioicous. Although both perichaetia and perigonia were found on separate stem fragments, the stems are very brittle and it was impossible to prove that the two had not been part of a single plant.
Diploneuron is probably most closely related to Pilotrichidium and Callicostella, both of which have short leaf cells. It differs, though, in the unique costal development. Additionally, it differs from most species of Callicostella in the smooth leaf cells, slenderly lanceolate-acuminate leaves, and subentire margins. From Pilotrichidium it differs in the lack of a hyalodermis, the lanceolate-acuminate leaves, and cells not papillose even at the margins. The habitat of Diploneuron, fairly dry limestone, is also unlike that of either Callicostella or Pilotrichidium. The monospecific genus, for a Jamaican and Cuban endemic, was reviewed by Allen and Crosby (1986a).