Rhynchostegiopsis flexuosa (Sull.) Müll.Hal.

Authority

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

Family

Leucomiaceae

Scientific Name

Rhynchostegiopsis flexuosa (Sull.) Müll.Hal.

Description

Species Description - Plants slender to medium-sized, in lustrous, mostly bright- to yellow-green, occasionally whitish green, often dense but small mats. Stems creeping, to ca. 3 cm long, fragile, subpinnately to irregularly branched, ± complanate-foliate; in cross-section all cells thin-walled, the outer ones sometimes somewhat smaller than inner ones, central strand none; pseudoparaphyllia none; axillary hairs 2-celled, with a short brown basal cell and an elongate hyaline distal cell. Leaves ± contorted wet or dry, sometimes falcate, densely foliate, erect-spreading to spreading, ± complanate when dry, only obscurely so when moist, dorsal leaves sometimes somewhat broader than lateral leaves but otherwise not differentiated, lanceolate to oblong-lanceolate, sometimes broadly so, 1.1 -2(-2.5) mm long, gradually long- and flexuose-acuminate, concave; margins obscurely bordered by a single row of broad, pellucid cells, especially obvious at base of acumen, serrulate to serrate above, more strongly so in the acumen, entire below, plane or irregularly erect; costa none or occasionally short and double; cells long-hexagonal to sublinear, ca. 10:1, lax, smooth, thin-walled, somewhat longer in the acumen, becoming short and irregularly rectangular in 1-2 rows across the insertion; alar cells not differentiated. Asexual propagula none. Dioicous, but commonly fertile. Perichaetia elongate, fairly conspicuous; leaves erect with spreading apices, lanceolate, 0.85-1.4 mm long, gradually long-acuminate; margins not bordered, serrulate (to serrate) above, entire below, plane; costa none; cells as in vegetative leaves. Setae very long, smooth except slightly roughened just at base of capsule, reddish, 1-3 cm long, curved at apex; capsules inclined to pendent, short-cylindric, 0.75-1.5 mm long, somewhat arcuate, slightly roughened at neck; exothecial cells subquadrate, thin- to firm-walled, ± collenchymatous; annulus of 2-5 rows of pale, oblate, thin-walled cells, deciduous; operculum long-rostrate, somewhat oblique; exostome teeth yellowish, narrowly triangular, narrowly bordered, not shouldered, on the front surface with a narrow but well-defined pale median furrow with a zig-zag line down it, the plates densely cross-striolate below, coarsely papillose above, slightly trabeculate at back, smooth to finely papillose; endostome with a fairly high, smooth basal membrane, segments finely papillose-spiculose, keeled, not or narrowly perforate, with baffle-like crosswalls, ca. as long as the teeth, cilia in groups of l-2(-3), obscurely nodose, faintly roughened, shorter than the segments. Spores spherical, finely papillose, 12-15 µm diam. Calyptrae cucullate, split 2/3 its length, ± entire at base (irregular but not lobed), naked, smooth.

Discussion

1. Rhynchostegiopsis flexuosa (Sull.) Müll. Hal., Nuovo Giorn. Bot. Ital. II, 4: 163. 1897; Hypnum flexuosum Sulk, Proc. Amer. Acad. Arts 5: 288. 1861; Leucomium flexuosum (Sull.) Mitt., J. Linn. Soc., Bot. 12: 501. 1869. Plate 37, figures 1-7 Leucomium serratum Besch., J. Bot. (Morot) 8: 179. 1894; Rhynchostegiopsis serrata (Besch.) Broth, in Engl. & Prantl, Nat. Pflanzenfam. 1(3): 948. 1907. Discussion. Rhynchostegiopsis flexuosa is distinctive in its somewhat falcate leaves that are laxly areolate and ecostate. The upper margins are usually serrate and the leaf apex is often flexuose or zig-zag. The setae are long, to 3 cm; the exostome teeth are narrowly furrowed; and the calyptrae are cucullate. It is readily separated from its only congener in the West Indies, R. tunguraguana, by its smaller stature and more elongate leaf apex. Hasty examination may result in confusion with Trachyxiphium guaclalupense, but that species has a strong, double costa and swollen marginal teeth, among other, less obvious differences. Rhynchostegiopsis serrata supposedly differs in sexuality (autoicous) and seta length (short). However, a portion of the type I examined was sterile, and so I was unable to verify these differences. Seta length, though, among dioicous plants with typically elongate setae, can sometimes be quite short (usually on depauperate collections). Since R. flexuosa is often fertile, despite its dioicy, perhaps the report of autoicy in R. serrata is in error. Gametophytically, there is nothing worthy of recognition.

Distribution

Range. Mexico to Costa Rica; Cuba, Jamaica, Hispaniola (Haiti and Dominican Republic), Puerto Rico, Guadeloupe, Dominica; usually growing on wood (roots, twigs, rotten logs), in humid forests, at 350-1500 m.

Mexico North America| Guatemala Central America| Belize Central America| El Salvador Central America| Honduras Central America| Nicaragua Central America| Costa Rica South America| Cuba South America| Jamaica South America| Haiti South America| Dominican Republic South America| Puerto Rico South America| Guadeloupe South America| Dominica South America|