Stenodictyon

• Authority

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

• Family

  Pilotrichaceae

• Scientific Name

  Stenodictyon

• Description

  Genus Description - Plants medium-sized to robust, in lustrous, yellow-green to brownish, thin but often extensive mats. Stems creeping to scrambling, irregularly branched, not complanate-foliate; in cross-section with a unistratose hyalodermis over small thick-walled cells surrounding large thin-walled cells, central strand none; rhizoids tufted on basal portions of stems, slightly roughened; pseudoparaphyllia none; axillary hairs 2-celled, with a short brown basal cell and an elongate hyaline distal cell. Leaves uniform, not particularly contorted when dry, not complanate, densely foliate, ovate, oblong-ovate, or oblong-lanceolate, concave, ± gradually or more typically abruptly slenderly acuminate from an obtuse leaf apex, the acumen sometimes flexuose; margins not or obscurely bordered by elongate, narrow cells, subserrulate in the acumen and at acumen-lamina junction, entire below, plane or often narrowly recurved; costa double, ending near midleaf, not projecting at apex; cells long-hexagonal to sublinear, smooth, thin- to firm-walled, sometimes porose, becoming shorter, broader, firmer-walled, and colored toward the insertion; alar cells not differentiated. Asexual propagula not seen. Dioicous or autoicous. Perichaetia small, inconspicuous, on older stems; leaves erect, oblong-ovate, abruptly long-awned from an obtuse apex; margins not bordered, serrulate in the acumen, often with a few coarse teeth at base of acumen, entire below, plane; costa none; areolation similar to that of vegetative leaves. Setae elongate, often very long, smooth throughout or slightly roughened at extreme apex, reddish, curved at apex; capsules inclined to pendent, broadly cylindric, symmetric, neck not or scarcely differentiated; exothecial cells subquadrate to short-rectangular, sometimes collenchymatous; annulus not differentiated; operculum conic long-rostrate, the basal cells differentiated with the bottom-most row ± thin-walled and inflated with several rows above it of ± quadrate, pale, nodose-walled cells; columella globular to turbinate, very short; peristome double, attached at the mouth, exostome teeth narrowly triangular, narrowly bordered, not shouldered, on the front surface with a broad, pale furrow with a zig-zag line down it, the plates densely cross-striolate below, papillose above, slightly trabeculate at back; endostome with a medium-high to fairly high basal membrane, segments keeled, not or narrowly perforate, with baffle-like crosswalls, ca. as long as the teeth, cilia none. Spores spherical, finely papillose, mediumsized to large. Calyptrae mitrate, lobed and plicate at base, naked, smooth.

• Discussion

  Stenodictyon (Mitt.) A. Jaeger, Ber. Thätigk. St. Gallischen Naturwiss. Ges. 1875-76: 358. 1877; Hookeria sect. Stenodic-tyon Mitt., J. Linn. Soc., Bot. 12: 348. 1869. Discussion. Stenodictyon is a small genus, limited in its distribution to higher elevations in northwestern South America and adjacent Central America and the Greater Antilles. It was revised by Allen et al. (1985). It is characterized by stems with a strongly differentiated hyalodermis, and ± oblong-ovate leaves that abruptly taper to a slender awn. The leaves are concave and, for the Pilotrichaceae, weakly bicostate. The leaf cells are elongate and mostly thin-walled. The setae are very long and essentially smooth. The exostome teeth are furrowed and cross-striolate on the front surface. The calyptra is mitrate, naked, and smooth. When described, Stenodictyon was considered close to Stenodesmus, but that genus has an erect capsule on a spinose seta and a nonfurrowed, papillose exostome. Gametophytically the two genera are very similar indeed, presenting a comparable situation to that of Lepidopilum and Lepidopilidium. Both Stenodictyon and Stenodesmus have a differentiated hyalodermis, oblong leaves with an abruptly tapered, slender acumen, weak costae, and similar areolation. In the West Indies Stenodictyon may be confused, when sterile, with Lepidopilum. However, in that genus the plants are strongly flattened, unlike in Stenodictyon. Rhynchostegiopsis may also be confused with Stenodictyon, but it has gradually acuminate, ecostate, and sharply serrate leaves. In the West Indies there is only one species in the genus.