6. Ditrichum heteromallum (Hedw.) Britt. 牛毛藓 niu-mao xian
N. Amer. Fl. 15: 64. 1913. Weissia heteromalla Hedw., Sp. Musc. Frond. 71. 1801. Syntypes. Austria and Switzerland.
Ditrichum homomallum (Hedw.) Hampe, Flora 50: 182. 1867. Didymodon homomallus Hedw., Sp. Musc. Frond. 105. 1801.
Ditrichum subtortile Card., Bull. Herb. Boiss., sér. 2, 7: 716. 1907.
Plants small, up to 1.0 cm high, yellowish green, in loose tufts. Stems erect, simple. Leaves slightly homomallous, appressed when dry, erect-patent when moist, lanceolate, 2.0–3.5 mm long, abruptly narrowed from an ovate base to a long, setaceous acumen; margins plane and entire; costa stout, percurrent to short-excurrent, filling almost the entire subula; cells elongate throughout, rectangular to linear, 20–40 µm × 3–5 µm, rather thin-walled. Dioicous. Perichaetial leaves larger than the upper stem leaves, sheathing at base. Setae straight, 1.5–2.0 cm long, reddish brown; capsules erect, cylindric, nearly symmetric, ca. 2 mm × 0.3–0.4 mm, reddish brown, slightly contracted below the mouth; opercula short conic-rostrate; annuli in 2 rows of large, thick-walled cells; peristome teeth linear, 250–300 µm long, divided nearly to the base, whitish yellow, irregularly papillose. Spores 10–12 µm in diameter, yellow, nearly smooth.