Cyclodictyon

• Authority

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

• Family

  Pilotrichaceae

• Scientific Name

  Cyclodictyon

• Description

  Genus Description - Plants slender to rather robust, in often lustrous, whitish green to golden-brown, mostly complanate, dense to lax mats. Stems creeping, irregularly branched, the branches not differentiated, complanate-foliate; in cross-section with a unistratose hyalodermis over firm-walled medium-sized cells surrounding large thin-walled cells, central strand none; rhizoids confined to oldest parts of stems, tufted, smooth; pseudoparaphyllia foliose, evanescent; axillary hairs 2-celled, both hyaline, with a short basal one and an elongate apical one. Lateral and dorsal leaves differentiated in shape and orientation, lateral leaves mostly wide-spreading, broadly oblong, broadly triangular, ovate or lanceolate, mostly asymmetric, acuminate to apiculate, sometimes from a broadly rounded apex, dorsal leaves erect to erect-spreading, lanceolate to ovate, mostly symmetric, acuminate to mucronate, all usually closely foliate, sometimes contorted when dry, margins bordered by 1 to several rows of narrow, short or elongate cells, usually broader below, subentire to serrate, mostly serrulate, mostly plane, sometimes narrowly recurved; costa double, strong, ± divergent throughout, ending 1/2-4/5 the leaf length, sometimes projecting at apex; cells often ± isodiametric, commonly hexagonal, sometimes ± elongate, upper ones rarely more than 3.1, smooth, typically thin-walled, sometimes firm-walled, usually becoming longer and long-rectangular toward insertion; alar cells not differentiated. Asexual propagula unknown. Autoicous, synoicous, or dioicous. Perichaetia small, inconspicuous, along stems; leaves few, pale, erect, lanceolate to lanceolate-triangular, acuminate; margins obscurely to distinctly bordered with narrow, elongate cells, serrulate above, entire below, plane; costa double, less developed than in vegetative leaves, divergent, usually not projecting at apex, sometimes single or none; cells mostly long-hexagonal throughout. Setae elongate, smooth, reddish, usually curved at extreme apex, twisted; capsules inclined to horizontal to ± pendent, oval to cylindric, often curved, asymmetric; exothecial cells ± quadrate, the horizontal walls thinner than the vertical ones, obscurely collenchymatous; annulus ± none (with a single row of short, thin-walled, ± inflated cells adhering to inside of operculum); operculum conic-long-rostrate, the rostrum often pale; columella short, not exserted; peristome double, attached at the mouth, exostome teeth triangular, ± bordered, not shouldered, on the front surface reddish, with a broad median furrow with an included zig-zag line, cross-striolate except coarsely papillose at extreme apex, at back trabeculate, yellow; endostome yellowish, smooth to finely papillose, with a relatively high basal membrane, segments keeled, not or narrowly perforate, with baffle-like crosswalls, ca. as long as the teeth, cilia none or short and single. Spores spherical, finely roughened, small. Calyptrae mitrate, covering most of the capsule and often constricted below the urn, lobed at base, naked, smooth or roughened.

• Discussion

  Discussion. Cyclodictyon is probably the easiest genus to recognize in the family. The leaves are bordered by elongate, narrow cells that contrast sharply with the large, lax laminai cells. The costa is double and usually extends over half the leaf length. The plants are complanate-foliate and often whitish. The capsules are smallish, inclined and asymmetric. Until maturity the mitrate calyptra covers the capsule and is constricted at its base at the junction of the urn and seta. The exostome teeth are strongly and conspicuously furrowed. The genus is fairly speciose and best represented in the New World tropics. The combination of prostrate, complanate-foliate plants with strong, double costae and bordered leaves is unique in the Hookeriales. Fortunately, most of the taxa occurring in the West Indies were described fairly early so that most competing South and Central American names are more recent and not likely to displace the epithets used here. Although its strong leaf border is unique in the Pilotrichaceae (that of Lepidopilum is not nearly as discrete), the double costa, 2-celled axillary hairs, and hyalodermis seem to relate Cyclodictyon to Thamniopsis. At the other end of the genus the aquatic species are indeed similar to the bordered (and sometimes aquatic) species of Lepidopilum.