Gymnostomum prorepens Hedwig, Sp. Musc. Frond., 35, plate 3 [top], figs. 1-4. 1801; Drummondia canadensis (Kindberg) Macoun & Kindberg; D. clavellata (Hooker & Greville) Hooker; D. clavellata var. canadensis Kindberg

Plants olive green, dark green, or yellow-brown. Stem leaves channeled, concave, 1.1-1.8 mm; apex sometimes incurved; costa broadly channeled; alar cells yellow, ± inflated at marginal insertion; basal laminal cells 6-10 µm. Perichaetial leaves closely clasping seta, broadly lanceolate, to 2 mm, apex acute or acuminate, basal laminal cells rectangular, yellowish green. Seta dextrorse. Capsule 0.9-1.3 mm, sharply contracted to seta, neck absent; exostome teeth 3-6 cells high, rudimentary, truncate. Spores rounded-quadrate to elliptic-rectangular, 70-100 µm in longest dimension, almost smooth, brown.

Trunks and branches of deciduous trees, dry, upland forests, cedar glades, conifers, logs; low to moderate elevations; N.B., N.S., Ont., Que.; Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., Maine, Md., Mass., Mich., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Vt., Va., W. Va.

Drummondia prorepens is characterized by long, creeping stems with many erect branches bearing terminal sporophytes. This habit, combined with the cucullate calyptrae, the smooth, ovate capsules with 16 truncate exostome teeth, the lack of stomata, and the undifferentiated basal laminal cells, is absolutely diagnostic.