3. Pylaisia selwynii Kindberg, Ottawa Naturalist. 2: 156. 1889. (as selwyni).
Pylaisia schimperi Cardot; Pylaisiella selwynii (Kindberg) H. A. Crum, Steere & L. E. Anderson
Plants yellowish to whitish. Stems terete-foliate to flattened, regularly and densely pinnate, branches 3 mm, ascending, strongly curved, subjulaceous; pseudoparaphyllia triangular, strongly dentate. Stem and branch leaves differentiated. Stem leaves almost straight, broadly ovate-lanceolate, suddenly narrowed to apex, not concave, not plicate, 0.9-1.2 × 0.5-0.6 mm; margins plane, sometimes slightly incurved distally; acumen short; costa double and short or indistinct; alar cells 20-25 along margins, in 6-10 rows; medial laminal cells 25-45 × 4-7 µm. Branch leaves oblong-lanceolate, smaller, narrower, 0.7-0.9 × 0.2-0.3 mm. Seta 1-1.5 cm. Capsule erect to suberect, oblong-ovoid, 1-1.6 × 0.6 mm; exothecial cell shape variable; operculum conic; peristome somewhat reduced; exostome teeth lanceolate, 0.1-0.2 mm, base 45-50 µm wide, finely papillose distally; endostome adherent to exostome teeth except distally, basal membrane developed except distally, segments 2-fid, split, internal surface roughly and finely papillose, segment and cilia connate. Spores 16-25 µm.
Capsules mature fall. Tree trunks; moderate to high elevations; N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., Que., Yukon; Ala., Alaska, Ariz., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., Vt., Va., W.Va., Wis.; Mexico; Asia (sw China, Japan, Russia).
Pylaisia selwynii is the most frequent and common species of the genus in the flora area; it is easily distinguished by the regularly and densely pinnate stems, broadly ovate-lanceolate stem leaves, comparatively numerous alar cells of the stem leaves, and adherent endostomes except for the distal portion. The stem leaves are secund and cordate.