Anoectangium laetevirens Besch. & Card., Bull.

Anoectangium laetevirens Besch. & Card., Bull. Herb. Boissier, sér. 2, 7: 712. 1907. Type: Japan “Japon: Yezo (n. 599); Kofu (n. 2552). Corée: île Quelpaert (n. 5, 6, 74, 80)” (not seen, one of syntypes illustrated by Saito, 1975, figs. 34–16). Plants small, in dense tufts or cusions, yellowishgreen in upper part, dark brownish below. Stems 1–2 cm, erect, simple or rarely forked. Leaves densely arranged and hiding the stem, contorted when dry, sometimes slightly spirally twisted, patent when wet, narrowly lanceolate, widest at or above mid-leaf, narrowed to the base, acute, strongly keeled, carinate, (0.45–)0.8–1.3(–1.6) mm long, 0.14–0.28 mm wide; margins plane, entire; costa +strong, 30–35 µm wide at base, excurrent into short apiculus to 3–4 cells long or percurrent, densely or loosely papillose dorsally in distal 2/3; upper and median laminal cells rounded-quadrate or transversely elliptical, 6– 8×7–12 µm, +thick-walled, opaque, densely covered by massive, low, bifid papillae; basal juxtacostal cells smooth, with moderately thickened walls, short rectangular, 12– 20×6–11 µm, becoming quadrate and transversely rectangular towards margins. Gametangia and sporophytes unknown in Russia. [Perichaetial leaves broad-ovate, narrowly acute at apex, 0.5–0.7 mm long, 0.3–0.4 mm wide at middle. Setae 3–5 mm long. Capsule short-cylindrical, 0.6–0.8 mm long, ca. 0.4 mm thick at middle. Opercum 0.7 mm long. Spores 9–12 µm (Saito, 1975)]. Specimens examined: RUSSIA: Primorsky Territory: Olga District, waterfall on Milogradovka Creek, 310–370 m alt., Ignatov #07-311, 07-295 (MW9001560, MW9001559); Sakhalinslaya Province, South Kuril Islands, Shikotan Island, Notoro Mt., 320 m alt., Bakalin K-42-28-07 (MW9001567); same place, area of Tomari Mt., 300 m alt., Bakalin K-45-13-07 (MW9001568) and Bakalin K-45-3-07 (MW9001569); JAPAN, Kyushu, Miyazaki Prefecture, Inohae Valley, Ignatov & Ignatova 98-509 (MW9001570). Differentiation. Anoectangium laetevirens is similar to A. aestivum in plant size and leaves lacking constriction above their bases, but differs from it in leaf arrangement (dense, hiding stem vs. + spaced, exposing stem at places); leaf shape (widest above mid-leaf, not widened at base vs. widest below mid-leaf, usually widened at base); and costa length (percurrent or excurrent into short mucro vs. ending below apex). Ignatova (2009) tentatively referred these specimens to A. stracheyanum despite the absence of constriction in their leaves, considering them as an extreme variation of the latter species in harsh environments, but the present study confirms their separate species identity. The distinctions of A. laetevirens from A. stracheyanum include smaller size of plants, shorter and narrower leaves and absence of constriction above leaf base. Distribution and ecology. In Russia, A. laetevirens occurs mostly in Kuril Islands; its single locality in the mainland is in a valley near waterfall (albeit not very big one), providing high and constant air humidity, where some other rare mosses were found.