Pylaisia subcircinata Cardot, Bull. Soc. Bot.

9. Pylaisia subcircinata Cardot, Bull. Soc. Bot. View in CoL

Genève 3: 287. 1911.

Figs. 27 View Fig , 28 View Fig , 34J View Fig .

Description. Plants small to medium-sized. Stems and branches straight to curved, loosely to densely foliate; leaves homomallous, turned outwards substrate. Stem leaves falcate, 0.8–1.2× 0.3–0.5 mm, from ovate-triangular base gradually tapered to narrowly lanceolate acumina; margins subentire; median laminal cells 45– 80×4–6 µm, alar cells subquadrate and transversaly rectangular, in a small group, 7–10 cells long and ca. 10 cells wide. Branch leaves smaller, lanceolate. Capsules ovoid-cylindrical. Operculum long-rostrate. Peristome in dry state forms low conus due to adherence of its elements. Exostome teeth to 200 µm long, dorsal plates smooth below, slighlty papillose above; endostome adherent to exostome teeth almost thoughout its length, except the upper part; segments rather broad, shortly exserted above teeth ends; endostome slightly papillose. Spores 25–32 µm.

Differentiation. This species has leaves that are similar to P. brotheri in ovate-triangular basal part shape and gradual tapering to acumen. However, leaves of P. brotheri are only slightly curved, whereas in P. subcircinata they are falcate to almost circinate. The most distinctive feature of P. subcircinata is a small alar group, often broader than long that differentiate this species from P. brotheri and P. condensata , but makes it more similar to P. obtusa , a species that appeared most closely related to P. subcircinata basing on our molecular phylogenetic reconstruction. This similarity led to a number of misidentifications in herbaria, as P. obtusa is often superficially rather similar and has homomallous to falcate leaves when they are attached to stem. However, in microscope slides leaves of P. obtusa are straight, with ovate basal part, while leaves of P. circinata are strongly curved and have triangular basal part. The easiest way to distinguish P. circinata from P. obtusa is checking the opeculum shape: long rostate vs. short and blunt, but as the capsules appear in late autumn, this character cannot be observed in some specimens.

Distribution. Pylaisia subcircinata is common in Japan and know from Korea ( Arikawa, 2004). It is apparently a rare species in Russia: Bardunov & Cherdantseva (1982) cited it only from one locality in Primorsky Territory; Cherdantseva (1976) listed it for Sakhalin based only on the record of Sakurai (1935), and Bardunov & Cherdantseva (1984) reported it from few localities in Kuril Islands (Kunashir and Shikotan). Chernyadjeva (2012) reported this species as sporadic in Kamchatka; however, it was likely based on misidentification of P. obtusa .

Specimens examined: RUSSIA: Primorsky Territory,

Lazovsky Reserve, Perekatnaya Creek, 21 Sept. 1974, Bardunov s.n. (ex IRK, MHA9130434); Sakhalinskaya Province: Kuril Islands, Shikotan Island, area of Malokurilsk Village, Bakalin K-37-48-07 (ex VLA, MW9061987); Sakhalin, Dolinsky Distr., mouth of Bakhura River, 19 Jul. 2001, Cherdantseva s.n. (ex VLA, MHA).