Hypnum delicatulum Hedwig, Sp. Musc. Frond., 260. 1801; Thuidium recognitum var. delicatulum (Hedwig) Warnstorf

Plants green or yellowish brown. Stems 3-8 cm, 2- or 3-pinnate, ± frondose; paraphyllia usually papillose at cell ends. Stem leaves erect, appressed when dry, erect-spreading when moist, triangular-ovate, not plicate, 0.6-1.5 mm; margins revolute throughout, papillose- serrulate; apex acuminate; costa ending well before apex; distal laminal cells irregularly oblong-hexagonal or rhombic, 6-10 × 8-12 µm, . Branch leaves with apical cell truncate, multipapillose. Primary branch leaves to 0.5 mm; costa 1/2-2/3 leaf length. Secondary branch leaves 0.3 mm; apex acute; costa to 1/2 leaf length. Perichaetial leaves to 5 mm, margins not ciliate to ciliate proximally, often denticulate distally. Seta 1.5-4.5 cm. Capsule 1.8-4 mm; operculum 0.7-2 mm, long-rostrate; endostome cilia in groups of 2 or 3. Spores 12-24 µm, smooth.

Varieties 10 (2 in the flora): North America, Mexico, Central America, n South America, Europe, Asia.

Thuidium delicatulum, if confused with T. recognitum, can be recognized by the stem leaves erect or erect-spreading when moist, not plicate and rather gradually acuminate, with margins recurved to the base of the acumen and costa ending well before the apex. The paraphyllia have small papillae along the cell midpoints. The laminal cells are stoutly 1-papillose, but often, especially in the South, the papillae are 2-fid. The branch leaf laminal cells are rhombic, 6-8 × 8-12 µm, with curved papillae.