Leptodontium flexifolium Hampe ex Lindberg 1864

Leptodontium flexifolium is a rare species found in rocky places at higher elevations in the southern Appalachians and in the southwestern states. The gemmae that are commonly found on stalks in leaf axils elsewhere were not seen in the flora area. The dentate, bordered leaves are immediately diagnostic of this species, while the anatomical characters of the genus will confirm the identification. Subfossils 40,000 years old have been found (J. A. Janssens and R. H. Zander 1980) at a site in the Yukon. Dichodontium pellucidum is commonly mistaken for this species, but is easily distinguished by the dentate distal abaxial surface of the costa. Barbula convoluta is also similar but has quadrate adaxial costal cells and a distinct stem central strand.

Stems to 1 cm. Leaves 0.7-0.9 mm, ligulate to short-lanceolate, bordered distally by 1-5 rows of less papillose, thick-walled cells; apex broadly acute; costa ending 2-4 cells before the apex, abaxially papillose; distal laminal cells 10-12 µm wide, 1:1, walls thin in medial portion of leaf, lumens quadrate, proximal cells thin-walled throughout.

Plants small, thick, to 20 mm high, yellowish green, scattered or in loose tufts. Stems erect, simple or branched, densely foliate, sparsely radiculose at base. Leaves erect to somewhat involute when dry, erect- to wide-spreading when moist, oblong-ovate, 1.2–1.8 mm × 0.3–0.5 mm, obtusely pointed to broadly acute; margins entire, recurved in the lower half, irregularly loosely dentate in the upper half; costa slender, ending just below the apex; upper leaf cells rounded-hexagonal, 10–14 µm × 8–12 µm, strongly thick-walled, with several simple papillae; basal cells irregularly to linear-rectangular, 30–55 µm × 10–20 µm, thin-walled, smooth, hyaline. Sporophytes unknown.

Distribution: China, Japan, India, Indonesia, New Guinea, Africa, Europe, and throughout America.

Habitat: on tree trunks, ground, or grasslands.

Bryum flexifolium Dickson, Fasc. Pl. Crypt. Brit. 4: [29]. 1801; Leptodontium flexifolium var. americanum (Grout) Grout; L. orcuttii E. B. Bartram; Zygodon gracilis var. americanum Grout

Bryoerythrophyllum dentatum (Mitt.) P.-C. Chen, Hedwigia 80: 253. 1941. Didymodon dentatus Mitt., J. Proc. Linn. Soc., Bot., Suppl. 1: 23. 1859. Bryoerythrophyllum pergemmascens (Broth.) P.-C. Chen, Hedwigia 80: 261. 1941. Leptodontium pergemmascens Broth., Akad. Wiss. Wien Sitzungsber., Math.-Naturwiss. Kl., Abt. 1: 133. 565. 1924. Bryoerythrophyllum yichunense C. Gao, Fl. Musc. Chin. Boreali-Orient. 379. f. 80. 1977, syn. nov. Type. China: Heilongjiang, Yi-chuan Co., P.-C. Chen & C. Gao 346 (holotype IFSBH). Leptodontium gracillimum Nog., J. Jap. Bot. 20: 142. 1945. Leptodontium nakaii Okamura, J. Coll. Sci. Imp. Univ. Tokyo 36(7): 9. 5 A–H. 1915. Leptodontium warnstorfii Fleisch., Musci Buitenzorg 1: 364, f. 67. 1904.