Chionoloma cf. cylindrotheca (Mitt.) M. Alonso, M. J. Cano & J. A. Jiménez, Ann. Missouri Bot. Gard.

Chionoloma cf. cylindrotheca (Mitt.) M. Alonso, M. J. Cano & J. A. Jiménez, Ann. Missouri Bot. Gard. View in CoL 194: 582. 2019. — Tortula cylindrotheca Mitt., J. Proc. Linn.

Soc., Bot., Suppl. 1: 30. 1859. — Oxystegus daldinianus (De Not.) Köckinger, O. Werner & Ros , Nova Hedwigia Beih. 138: 39. 2010. — Didymodon cylindricus (Brid.) Bruch & Schimp. var. daldinianus De Not., Atti Reale Univ. Genova 1: 563. 1869. Fig. 4.

Plants medium-sized, in low, dense or loose tufts, green or dark-green. Stems to 3(5) cm long, simple or branched, without hyalodermis and central strand. Leaves incurved and twisted when dry, erect spreading to patent when wet, not fragile, linear-lanceolate, 4–6× 0.5–0.6 mm, often cuspidate at apices, with short, canaliculate apiculi (at least in some leaves) or acute, with weakly differentiated bases; margins plane, entire or weakly papillose-crenulate, occasionally also distantly denticulate in upper and middle portion; costa strong, percurrent or short excurrent, 80–100 µm wide at leaf base, smooth on dorsal surface, papillose on ventral surface above base, in transverse section with one layer of guide cells, dorsal stereid band larger than ventral one or equal to it in size, with differentiated ventral epidermis and without dorsal epidermis; upper and median laminal cells quadrate and short transverse rectangular, 8–12(–15) µm wide, moderately densely papillose; basal laminal cells rectangular, 20–65×8–17 µm, smooth, hyaline; transition from hyaline basal cells to chlorophyllose median cells more or less abrupt, straight, not V-shaped. Dioicou s, sporophytes unknown in Russia.

Distribution and ecology. Chionoloma cylindrotheca was described from India; it occurs also in Nepal, Buthan, China, Japan, Malaisia, Thailand in Asia, in subatlantic and central regions of Europe, and eastern North America. In Russia it was known only in the western Caucasus, near Sochi. Its finding in Primorsky Territory could be expected, as it occurs in neighboring Japan and China; however, its presence here is confirmed by molecular barcoding for the first time. It was collect- ed in Khasansky District on southern slope of Mramornaya Mt., on rock outcrops under crooked oak canopy ( Fig. 6B View Fig ).

Differentiation. Alonso et al. (2019) consider the shape of leaf apex to be the main diagnostic character of C. cylindrotheca ; however, such attenuate, canaliculate apiculi are usually found only in some leaves of its plants. In some cases, it is very difficult to separate C. cylindrotheca from C. tenuirostre . The latter species possesses a combination of morphological characters similar to that of C. cylindrotheca , including linear-lanceolate leaves, costa with dorsal stereid band larger than ventral one, weakly differentiated leaf base, and border between hyaline basal cells and chlorophyllose median cells straight, not V-shaped. It is interesting to note that Alonso et al. (2019) do not mention leaf fragility among morphological characters of C. tenuirostre ; in the key to identification, they separate mainly tropical C. hyalinoblastum (Broth.) M. Alonso, M.J. Cano & J.A. Jiménez with strongly fragile leaves from C. tenuirostre with usually intact leaves. This contradicts the description of the latter species in some European and Russian handbooks ( Guerra, 2006; Hallingbäck et al., 2008; Savicz-Lyubitskaya & Smirnova, 1970; Ignatov & Ignatova, 2003), where its leaves are described and illustrated as having sinuose upper margins, with constrictions marking places of breaking. Actually, specimens of C. tenuirostre with strongly fragile leaves prevail in herbarium collections from Russia, and only in the Russian Far East and, partially, Transbaikalia, plants with non-fragile leaves were frequently collected. Both C. cylindrotheca and C. tenuirostre occasionally have distantly and faintly denticulate upper leaf margins. Dorsal surface of costa is always formed of elongate, smooth cells in C. cylindrotheca , but, according to Alonso et al. (2019) it can be smooth or papillose (throughout or only distally) in C. tenuirostre . Unfortunately, this characters not very helpful for separation these species in the Russian Far East, since most specimens of C. tenuirostre have costae with smooth dorsal surface. Thus, study of more leaves and evaluating shape of their apices is the only possibility to separate these species in doubtful cases.

Specimens examined: Primorsky Territory, Khasansky Distr., vicinity of Khasan Settl., Reid Pallady Bay southern shore, Mramornaya Mt. SW slope near ridge ( 42.56695N, 130.80278E, 170 m alt.), meadow with oaks, bushes and rock outcrops, on boulder covered by thin layer of soil with Lycopodioides tamariscina , Grimmia pilifera, Hypnum leptothallum and Campylopus subulatus , 21.IX.2024, Fedosov & Pisarenko (MW9133399*, isolate BF175).

Putative hybridogeneous species with C. tenuirostre :

Primorsky Territory, Khasansky Distr., vicinity of Khasan Settl., Reid Pallady Bay southern shore, Priozernaya Mt. NW slope ( 42.54342N, 130.70530E, 64 m alt.), meadow with, rock outcrops,in niche, 22.IX.2024, Fedosov & Pisarenko ( MW133390 View Materials *, isolate BF176) GoogleMaps .