Marsupella yakushimensis (Horik.) S.Hatt., Bull. Tokyo Sci. Mus. 11: 80, 1944

Bakalin, Vadim, Choi, Seung Se & Park, Seung Jin, 2021, Revision of Gymnomitriaceae (Marchantiophyta) in the Korean Peninsula, PhytoKeys 176, pp. 77-110 : 77

Marsupella yakushimensis (Horik.) S.Hatt., Bull. Tokyo Sci. Mus. 11: 80, 1944 Figure 8

Sphenolobus yakushimensis Basionym. Sphenolobus yakushimensis Horik., J. Sci. Hiroshima Univ., Ser. B, Div. 2, Bot. 2: 156, 1934

Type.

Japan. Kagoshima Pref., Yakushima Island , Horikawa, 11895 (not seen) .

Description.

Plants in loose patches, deep green-brown, yellow-brown, yellowish brownish, rarely with purple tint, (1.0)1.5-2.1 mm wide and 15.0-50.0 mm long, rigid. Rhizoids nearly absent to very sparse, colorless, obliquely spreading, however common in basal part of ventral branches and leafless stolons. Stem easily laterally and ventrally branched giving start to normal branches or geotropic leafless stolons; stem transversely elliptic in cross section 210.0-240.0 μm high and 250.0-320.0 μm wide, distinctly differentiated into strata, hyaloderm cell walls moderately thickened (but external wall thin), with small concave trigones, 17.0-25.0 μm along margin, scleroderm cells with very thick walls and visible median lamina, 12.0-17.0 μm in diameter, but with lumen disappearing or only 2.0-6.0 μm in diameter, inner cells with moderately thickened walls and moderate in size, concave trigones, 10.0-15.0 μm in diameter. Leaves strongly conduplicate and distichously arranged that gives ‘scapanioid’ appearance, contiguous to imbricate, as a rule enclosed one to another, obliquely spreading and transversely oriented, when flattened subquadrate, rectangular or obovate to suborbicular (mostly wider than long, but sometimes longer than wide), bistratose in lower 1/5-1/6 of the leaf length, 675.0-1250.0 μm long and 800.0-1500.0 μm wide, commonly dorsally secund, divided by γ -shaped sinus descending to 1/4-2/5 of leaf length into two equal to subequal lobes (either ventral or dorsal may be smaller), lobes gibbous, with obtuse to acute or rarely rounded apex. Cells in the midleaf subisodiametric to (mostly) oblong, 12.0-25.0 × 7.0-20.0 μm, strongly thick-walled, with moderate to small, concave trigones, cuticle smooth; cells along leaf margin 7.0-10.0 μm, thick-walled (but with much thinner external wall), with moderate in size, concave trigones; cells in lobe middle 10.0-17.0 × 8.0-15.0 μm, thick-walled, with small to moderate in size, concave trigones, cuticle smooth. Dioicous. Androecia intercalary, with 2-3 pairs of bracts, spoon-shaped, with revolute margin and commonly deflexed lobe ends. Perianth (only unfertilized were found) hidden within bracts, onion-shaped, perigynium the same length with perianth or slightly longer, with 2 pairs of bracts and 1-3 lateral and ventral subfloral innovations.

Ecology.

Acidophilic hygro- to hydrophyte. The species occurs on wet cliffs at a distance from watercourses or on stones washed with sluggishly running water in partly shaded habitats in the middle elevation of mountains covered with evergreen to deciduous broadleaved forests. Commonly, the species forms pure patches or rarer, associated with Scapania undulata .

Distribution.

South temperate to subtropical Montane East Asian endemic species known in China (Anhui, Fujian, Guangdong, Jiangxi, Zhejiang), the southern part of the Korean peninsula (the report by Kim and Hwang (1991) for North Korea is doubtful) and the southern half of Japan. The species was reported from Gyeongsangnam-do, Gangwon-do, Gyeongbuk-do ( Kim and Hwang 1991; Yamada and Choe 1997) and here added to Jeollabuk-do and Jeju-do. The specimen included in the phylogenetic tree in Bakalin et al. (2019) under the name Marsupella alata S.Hatt. et N.Kitag. (Republic of Korea, Seorak Mt., 11.V.2011, Bakalin, Kor-6-28a-11, VBGI) was re-studied and found as the dwarf modification of M. yakushimensis . Although the distinctive differences between cited specimen and another accession of M. yakushimensis may suspect more robust than infraspecific differences that should be considered in future studies of the genus in East Asia.

Specimens examined.

Gangwon-do: Mt. Seorak , 38°09'34.3"N, 128°28'10.5"E, 631 m, 11 Oct 2010, S.S. Choi 8347 (JNU); Gyeongsangnam-do: Mt. Jiri , 35°19'58.3"N, 127°44'27.5"E, 1327 m, 4 Oct 2011, S.S. Choi 111125 (JNU); Jeollabuk-do: Mt. Jiri, 35°19'25.0"N, 127°41'36.8"E, 1300 m, 7 Oct 2009, S.S. Choi 6083 (JNU), Mt. Jiri, S.S. Choi 1067 (JNU); Jeju-do: Seogwipo-si, 33°18'30"N, 126°30'30"E, 600-800 m alt. 13 May 2015, V.A. Bakalin s.n. (VBGI) .

Comments.

This large and beautiful species is a rarity within the Korean flora and is known only from a few localities. Unlike Japanese populations, the Korean populations acquire purple to red pigmentation as an exception. The main characteristic of the species includes nearly equal lobes that do not have recurved margins, but commonly undulate and/or turned antically. Another characteristic feature is the absence of a distinctly sheathing leaf base. Dwarf plants of M. yakushimensis may be mistaken for M. koreana , and the distinctions are given under the latter. This species is regularly observed with androecia and rarely with archegonia. Androecious and gynoecious plants were intermixed within two specimens; however, we were unable to observe fertilized (in at least two descendant generations) and fully developed perianth. Whether this is the norm or not is not clear.

Figures

Figure 8. Marsupella yakushimensis (Horik.) S. Hatt. A plant, dorsal view B stem cross section (fragment) C cells along leaf margin D midleaf cells E-H leaves. Scale bars: a 2 mm (A); b 1 mm (E-H); c 100 µm (B-D). All from Choi- 1067 (JNU).