BFNA Title: Clasmatodon
Author: D. H. Vitt
Date: October 9, 2009
Edit Level: R
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden
BFNA Web site: http://www.mobot.org/plantscience/BFNA/bfnamenu.htm

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XX. CLASMATODON Wilson, Kew. J. Bot. 4: 421. 1842 * [Greek clasmato, fragment, and odon, tooth, alluding to the endostome]

Dale H. Vitt

Plants small, slender, dull to bright green, in loosely interwoven, straggly mats. Stems prostrate, creeping, and irregularly branched; branch foliage similar to that of stem; axillary hairs 4--6-celled, distal cell obtuse, pale brown; juvenile branch leaves narrowly acute. Stem leaves ovate to ovate-lanceolate, acute to narrowly obtuse, concave, imbricate and ± subsecund, little decurrent; margins entire, subentire, to serrulate in distal 1/2, costa slender, reaching 1/3--2/3\x leaf length, ending without an abaxial spine; basal laminal cells quadrate to subquadrate, shorter at margins, in numerous rows, walls thin; laminal cells rhombic to oblong-rhombic, thin-walled, smooth. Branch leaves similar to stem leaves. Sexual condition autoicous; perichaetial leaves abruptly acuminate, erect to flexuose from sheathing base. Seta reddish, smooth. Capsule erect, narrowly elliptic to oblong, symmetric; annulus of 3--4 rows of small, brown cells, persistent; operculum long-rostrate; peristome double, of 16 short, slender, unequally 2-fid segments partially fused to inconspicuous basal membrane; exostome of 16, very short, blunt, partially fused teeth. Calyptra naked. Spores 14--21 µm, finely roughened.

Species 1: North America, Europe.

Clasmatodon has been variously placed in the Fabroniaceae or the Myriniaceae, but molecular data strongly suggest a position in the Brachytheciaceae as a small, epiphytic, monotypic genus with a reduced peristome.

1. Clasmatodon parvulus (Hampe) Sullivant in Gray, Man. Bot. No. U.S., ed. 2, 600. 1856

Leskea parvula Hampe, Linnaea 13: 46. 1839; Clasmatodon parvulus var. rupestris Lesquereux & James

Stems to 1(--2) cm, branches to 2(--5) mm. Stem leaves 0.4--0.7 x 0.3--0.5 mm; mid-leaf cells 18--30 x 8 --10 \um. Seta 2--5 mm. Capsule 0.7--1 mm.

Tree trunks and bases of trees, often in flood plain forests, or more rarely on calcareous rocks; 0--400 m; Ala., Ark., Fl., Ga., Ill., Ind., Ky., La., Md., Miss., Mo., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va.; Europe.

Clasmatodon parvulus forms small, slender, straggly mats largely on tree trunks of the southeastern U.S.A. In this habitat, it is characterized by a short costa (Leskea species have a strong costa ending near the apex), ovate, mostly bluntly acute leaves (Lindbergia has long-acuminate leaves), and the lack of erect, flagelliform branchlets (as has Platygyrium repens). The narrowly elliptic, erect capsule, with very reduced peristome, on a short seta is also diagnostic.