3. Platydictya subtilis (Hedwig) H. A. Crum, Michigan Bot. 3: 60. 1964. (as subtile).
Leskea subtilis Hedwig, Sp. Musc. Frond., 221. 1801; Amblystegiella subtilis (Hedwig) Loeske; Amblystegium subtile (Hedwig) Schimper; Serpoleskea subtilis (Hedwig) Loeske
Plants dense, green to brownish. Stems with branching angle wide, branches firmly attached; pseudoparaphyllia foliose; rhizoids below or at abaxial leaf insertion, red-brown, smooth. Leaves erect-spreading, often subsecund, 0.2-0.5 mm; base somewhat narrowed to insertion; margins entire or nearly so; alar cells subquadrate, region of 6-8+ cells; distal laminal cells oblong-rhomboid, (2-)3-5:1. Specialized asexual reproduction absent. Sexual condition autoicous; perichaetial leaf margins entire. Seta 0.7-1.2 cm. Capsule erect or nearly so, oblong-cylindric, symmetric, 1-1.5 mm, somewhat contracted at neck and sometimes below mouth when dry, neck short; stomata in neck; annulus 1-seriate; operculum conic, obliquely short-pointed to rostellate; exostome teeth yellow-brown; endostome cilia or 2, rudimentary or absent. Spores 9-13 µm.
Bark at base of hardwoods, exposed roots, logs; low to moderate elevations; N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que., Yukon; Ariz., Ark., Ind., Maine, Mass., Mich., Mo., N.H., N.J., N.Y., N.C., Okla., Vt., Va., Wis.; South America; Europe; Asia.
Distinctive features of Platydictya subtilis include the entire leaf margins, elongate distal cells, and many subquadrate alar cells; the capsule is erect or nearly so. This is the only species of the genus typically found on bark.