Diploneuron connivens E.B.Bartram
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Authority
Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
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Family
Pilotrichaceae
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Scientific Name
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Description
Species Description - Plants medium-sized, in dull or slightly lustrous, dark-green to golden, thin mats. Stems creeping, to ca. 3 cm long, brittle, intricately branched, tightly adnate to substrate; in cross-section with 3-6 rows of medium-sized ± thick-walled cells surrounding larger firm-walled cells, central strand none; 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, spreading to wide-spreading when dry, ± spreading when moist, lanceolate to oblong-lanceolate, 2-3.5 mm long, broadly acuminate, concave, rounded to the insertion; margins not bordered, entire to crenulate, the extreme apex sometimes serrulate, plane; costa double, strong, broad, diverging to leaf margin just below midleaf and then running along it forming a 4-5-stratose border, sometimes with bistratose border somewhat below merger of costa and margin, fusing above and filling the subula; cells oval to irregularly angled, 1-3(-5): 1, 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, 1.8-2.2 mm long, ± abruptly broad-acuminate; margins serrulate above, entire below, plane; costa double, broad, ± parallel after slightly diverging below, then converging at midleaf and running parallel to margin, forming thickened border, fusing above and filling the acumen; cells long-hexagonal to linear, 6-10:1, smooth, firm-walled, porose, becoming longer, broader, thinner-walled and nonporose toward insertion. Setae elongate, smooth throughout or slightly roughened at apex, reddish, 1.4-2 cm long, twisted, curved at extreme apex; capsules inclined to horizontal, cylindric, 1.5-2.5 mm long, symmetric; exothecial cells subquadrate to short-rectangular, thin-walled at surface, with collenchymatous thickenings below the surface; annulus none; operculum conic-rostrate, the rostrum fairly short, often pale; 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 with a relatively high, finely and sparsely papillose basal membrane, segments finely papillose below, spiculose above, keeled, perforate, with baffle-like crosswalls, cilia none. Spores spherical, finely papillose, 11-17 µm diam. Calyptrae mitrate, only covering operculum and apex of urn, lobed at base, sparsely hairy, the hairs uniseriate, hyaline, 8-12 cells long, smooth.
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Discussion
Harpophyllum subulatum E. Britton, Bryologist 17: 8. 1914, nom. inval. Discussion. Diploneuron connivens is immediately recognized by the double costa that forms a thickened border above, and then fuses to fill the broad acumen. The plants grow fairly tightly adnate, by rhizoidal tufts, to limestone. The brittle stems often break when the plants are collected. The exothecial cells of Diploneuron are particularly interesting. In most hookerioid mosses with collenchymatous exothecial cells, the thickenings are only at a single point where the radial, transverse, and outer tangential walls meet. This can be verified by focusing down through the cells and having the thickenings disappear. However, in Diploneuron connivens the thickenings are at the junction of the radial, transverse, and inner tangential walls. Therefore, from surface view the cells appear thin-walled, but the collenchymatous thickenings can be seen by focusing through the exo-thecium. Although Bartram (1936) described and illustrated Diploneuron as having a bistratose lamina, I was unable to verify this. In all my sections, the lamina is consistently unistratose except when the costa approaches the margin, in which case the small area of lamina between the costa and the margin is bistratose.
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Distribution
Range. Cuba, Jamaica; growing on relatively dry limestone, in open, often secondary, humid forests, below 500 m.
Cuba South America| Jamaica South America|