1. Platylomella lescurii (Sullivant) A. L. Andrews, Bryologist. 53: 58. 1950.
Hypnum lescurii Sullivant in A. Gray, Manual ed. 2, 679. 1856; Amblystegium lescurii (Sullivant) Austin; Sciaromium lescurii (Sullivant) Brotherus
Plants in fine sods or loose mats. Stems 1-6(-10) cm, brownish black, prostrate, defoliate proximally, branches 1-2 cm, ascending, simple; paraphyllia becoming scarce in emergent plants; pseudoparaphyllia foliose; rhizoids matted, brown. Stem leaves somewhat contorted when dry, 0.5-1.3(-1.5) mm; limbidia sometimes disappearing before acumen or base, sometimes with spurs extending into lamina; costa 40-60(-75) µm wide at base; basal laminal cell walls thick, sometimes pitted. Perichaetia with leaves lanceolate, 0.5-0.8 mm, margins serrulate, apex acuminate, costate. Seta single, yellow to reddish brown, 1-3 cm, straight or flexuose, tortuose in aquatic plants. Capsule reddish brown, 1.5-3 mm, usually shrunken below mouth when dry; exothecial cells rectangular; stomata superficial; annulus deciduous, 2- or 3-seriate; operculum conic-apiculate; exostome teeth 16, yellowish brown, lanceolate, external surface cross striolate proximally, papillose distally, internal surface trabeculate; endostome pale yellow, basal membrane high, papillose. Calyptra yellow. Spores finely papillose, yellowish brown.
Capsules mature spring-early summer. Wet rock, tree roots, rotting wood, base of trees along streams, waterfalls, seeps, submerged or in splash zone, lowland and montane deciduous or mixed deciduous-coniferous forests, acid and calcareous rock; low to moderate elevations (0-1500 m); N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que.; Ala., Ark., Conn., Del., Fla., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Mo., N.H., N.J., N.Y., N.C., Okla., Pa., S.C., Tenn., Tex., Vt., Va., W. Va.
Platylomella lescurii is distinguished by its mostly 2-stratose margins, filiform paraphyllia, and saxicolous substrate in streams and seeps. Sciaromium laxirete Abramova & I. I. Abramov, listed provisionally by R. Ochyra (1987) as a synonym of Platylomella lescurii, is known only as a Pliocene fossil from Bashkiria, western Eurasia.