Rhaphidostichum acestrostegium (Sull.) W.R.Buck

Authority

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

Family

Sematophyllaceae

Scientific Name

Rhaphidostichum acestrostegium (Sull.) W.R.Buck

Description

Species Description - Plants small, in mostly lustrous, ± soft, yellow-green to reddish green, thin mats. Stems creeping, to ca. 2 cm long, dark red, freely but irregularly branched, the branches short, ascending; in cross-section with (1-)2-3 rows of small thick-walled colored cells surrounding a few large firm-walled cells, central strand absent; pseudoparaphyllia foliose; axillary hairs with a single short brown basal cell and 1(-2) elongate hyaline distal cells. Stem and branch leaves similar, erect-spreading, lanceolate to oblong-lanceolate, 0.8-1.65 mm long, abruptly slenderly long-loriform, the apex often twisted, concave; margins serrate-serrulate above (entire to serrulate in the stem leaves), entire to serrulate below, plane; costa very short and double or absent; cells linear-flexuose, smooth, firm-walled, porose; alar cells 2-3 in each basal angle, greatly enlarged and inflated, oval or rarely ± oblong, yellow to red-brown, sometimes ± curved to the insertion. Asexual propagula none. Autoicous. Perichaetia on stems and bases of branches; leaves erect, oblong-lanceolate, ca. 1.5 mm long, abruptly acuminate; margins strongly serrate almost to base, more strongly so above, plane; costa mostly none; cells large and lax, smooth, thick-walled, colored in lower 1/4-1/3 of leaf; alar cells not differentiated. Setae elongate, smooth, reddish, 0.6-1.1 cm long, curved just below the urn; capsules inclined, small, asymmetric, ovoid to short-cylindric, 0.5-0.9 mm long; exothecial cells subquadrate, strongly collenchymatous, becoming smaller and oblate in 1 (-2) rows at the mouth; annulus not differentiated; operculum obliquely and slenderly long-rostrate, usually longer than the urn; exostome teeth narrowly triangular, shouldered, bordered, on the front surface with a narrow median furrow, cross-striolate below, coarsely papillose above, trabeculate at back; endostome with a high basal membrane, segments papillose, narrow, keeled, perforate, almost as long as the teeth, cilia single. Spores spherical, finely papillose, 11.5-17.5 µm diam. Calyptrae cucullate, naked, roughened above.

Discussion

1. Rhaphidostichum acestrostegium (Sull.) W. R. Buck, Moscosoa 5; 190. 1989; Hypnum acestrostegium Sulk, Proc. Amer. Acad. Arts 5: 287. 1861; Sematophyllum acestrostegium (Sull.) Mitt., J. Linn. Soc., Bot. 12: 488. 1869, “acistrostegium”; Rhaphidostegium acestrostegium (Sull.) A. Jaeger, Ber. Thätigk. St. Gallischen Natur-wiss. Ges. 1876-77: 402. 1878, “acistrostegium”; Acroporium acestrostegium (Sull.) H. A. Crum & Steere, Bryologist 59: 253. 1956. Plate 143, figures 1-6 Rhaphidostegium helleri Renauld & Cardot, Bull. Soc. Roy. Bot. Belgique 41(1): 95. 1905; Rhaphidorrhynchium helleri (Renauld & Cardot) Broth, in Engl., Nat. Pflanzenfam., ed. 2, 11: 427. 1925. Rhaphidostegium microtheca Renauld & Cardot, Bull. Soc. Roy. Bot. Belgique 41(1): 96. 1905; Rhaphidorrhynchium microtheca (Renauld & Cardot) Broth, in Engl., Nat. Pflanzenfam., ed. 2, 11: 427. 1925. Discussion. Rhaphidostichum acestrostegium is immediately distinguishable under the dissecting microscope by the slender plants with leaf apices that appear as long, golden hair points. With higher magnification the apex is sharply serrate/serrulate and usually twisted. The plants are much smaller than R. schwaneckeanum and autoicous. However, a relationship of the two species is unmistakable. The furrowed exostome led to the species’ placement in Acroporium (Crum & Steere, 1956: 254).

Distribution

Range. Cuba, Puerto Rico; growing on rotten wood, tree trunks, and rocks, in moist forests, at 500-1700 m. Previous reports from Hispaniola were based on misdeterminations.

Cuba South America| Puerto Rico South America|