BFNA Title: Pterogonium
Author: M. Bourell
Date: Oct. 2001
Edit Level: R
Version: 2a

Bryophyte Flora of North America, Provisional Publication


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XX. PTEROGONIUM Swartz, Disp. Syst. Musc. Frond. Suec.: 26.1799 * [Greek pteron, feather, wing, fin, and gonio, angle, corner, possibly alluding to the papillae projecting from the cell ends]

Mona Bourell

Leaves broad, acute and serrulate, with costa absent, or if present, double and short (i.e., ending before leaf middle). Laminal cells papillose distally by projecting cell ends on abaxial surface.


Species 3 (1 in the flora): temperate regions of North America, South America, Europe, Africa, Asia.


1. Pterogonium gracile (Hedwig) Smith, English Botany 16: 1085. 1802


Pterigynandrum gracile Hedwig, Sp. Musc. Frond., 80. 1801


Plants forming loose coarse mats; dull yellow-green to brownish green. Stems 1.5--8 cm, prostrate; branches 0.5--2 cm, numerous, often closely pinnate, appearing fascicled, and secund-ascending, julaceous with strongly attenuate tips, sometimes with elongated flagelliform tips; paraphyllia absent. Leaves closely imbricate when dry, erect-spreading when moist; ovate, 0.5--2 x 0.25--1.2 mm; base cordate, slightly decurrent; proximal margin serrulate and inflexed, distal margin serrate and plane; apex acute, concolorous; costa absent or short and double, ending before midleaf. Laminal cells linear-rhomboidal, 15--46 x 5--8 \um, shorter near apex; thick-walled, prorate, especially in distal region of leaf; alar cells numerous, oblate to rounded, 6.5--10 \um, strongly differentiated, extending halfway up the margins. Sexual condition dioicous; perichaetia acicular in axils of branches, perichaetial leaves imbricate, elongate acuminate, sheathing at base, 2.5--3 x 0.7--0.8 mm, paraphyses 0.6--0.8 mm. Seta reddish brown, 8--12 mm, twisted, smooth. Capsule exserted, erect and symmetric, light brown, cylindric, 2--3 mm, smooth; annulus deciduous, 2--3 cells thick; operculum conic, 0.4--0.5 mm; peristome double, pale; exostome teeth 16, erect, linear-lanceolate, 0.3--0.4 mm, base horizontally striolate, distally with vertical or oblique lines, weakly papillose at tips; basal membrane low, endostome segments linear, 0.3--0.4 mm, weakly papillose; cilia absent. Calyptra not seen. Spores round, 11--18 \um, papillose, brown.


Capsule maturity not seasonal. Forested mountains, rocks and boulders, trunks and bases of hardwood trees, rarely on soil; 0--1100 m; B.C.; Calif., Oreg., Wash.; Brazil; Europe; sw Asia; Africa.


J. Podpěra (1954) reported Pterogonium from eastern Ontario, but, according to Ireland et al. (1987), the Canadian distribution is restricted to British Columbia. The calyptra is described as cucullate, with few hairs, by A. J. Grout (1928--1934, 3: 220). Pterogonium may be confused with Antitrichia californica, a moss that commonly grows with it. Pterogonium is distinguished microscopically from Antitrichia by the presence of papillose median leaf cells and a short double costa (or rarely none). Macroscopically, the leaf apices are plane (in A. californica the apices are recurved) and the papillose leaves give the plant a dull appearance. In addition, a common field character, when dry, is the closely pinnate branches of Pterogonium usually arching in the same direction resembling the arching toes of the foot of a bird. Pterogonium and Bestia longipes may also be confused. Bestia longipes never has attenuate branches; the leaves are somewhat plicate and recurved at the base; the leaf cells are smooth, the distal laminal cells are longer, up to 5:1, while the single costa extends at least to the midleaf. Pterogonium gracile is known to accumulate large amounts of heavy metals (L. Rasmussen 1975). Decline of populations in northern Europe has been attributed to air pollution. Monitoring populations in western North America may be worthwhile.




Grout, A. J., 1928--1940. Moss Flora of North America. 3 vols. Newfane, Vt. and New York.


Ireland, R. R., G. R. Brassard, W. B. Schofield, and D.H. Vitt. 1987. Checklist of the mosses of Canada II. Lindbergia 13: 1--62.


Podpěra, J. 1954. Conspectus Muscorum Europaeorum. Praha.


Rasmussen, L. 1975. The bryophytic epiphyte vegetation in the forest, Slotved Skov, northern Jutland. Lindbergia 3: 15--38.