LAUSR

Scapania schljakovii Potemkin was described from North District of Sikkim, India, where it was collected on a dripping acid cliff in a glacial valley above Yakche, N of Lachung, 27°43′09′′N, 88°44′47′′E, ca. 3180 m a.s.l. (Potemkin 2001). Until now it was known only from the type locality and from Yunnan Province of China (Ellis et al. 2015). In the course of study of Scapania (Dumort.) Dumort. collections by G. and S. Miehe from Bhutan, S. schljakovii was recorded for the first time for this country. Specimen examined. Bhutan, Lhuntse District, Mongar, Rhutong La E side, Abies densa–Rhododendron forests and scrub on SE-facing rock slopes, ungrazed, ca. 27°35′N, 91°00′E, 3400–3600 m a.s.l., 22 May 2000, leg. G. & S. Miehe 00-45-10 (LE); small tuft with admixture of Sphagnum sp., with broken perianth, and gemmae. Distribution, Ecology and Reproduction. China: Yunnan; Bhutan: Lhuntse District; India: N. Sikkim. Collections of S. schljakovii were made from wet acid rocks (‘acid’ mentioned for specimens from Bhutan and N. Sikkim), at 3180–3600 m a.s.l. The species location in Bhutan is close to the type locality, situated ca. 220 km eastwards and ca. 200–400 m higher than the location in Sikkim. The species apparently frequently produces gemmae and perianths, known from specimens from Yunnan and Bhutan, and Yunnan and N. Sikkim, respectively. Taxonomic notes and Gemmae description. A detailed description and graphic illustrations of S. schljakovii were provided by Potemkin (2001). Plants from Bhutan are similar to those from the type locality but differ in the presence of gemmae on apices of some shoots. Gemmae are found also in plants from Yunnan (MO-6230476, LE duplicate studied). Gemmae deep to light or brownish-purple, occasionally brownish, (1–)2–celled, 10–12(–15) × 21– 25(–28) μm (Bhutan collection) to (23)25–30(35) × 10–12.5 μm (Yunnan collection), with mostly parallel sides, diagnostically bacilliform (Figure 1A,C) and resemble gemmae of S. umbrosa (Schrad.) Dumort. Their formation on plants from Bhutan results in modification of mature leaves and development of lobe protrusions of evenly thick-walled cells (Figure 1B), whereas in plants from China gemmae formation does not cause changes of leaf shape. It is noteworthy that marginal leaf teeth of S. schljakovii are often fragile, sometimes hooked at the very tip and are very finely punctate papillose and that perianths were found in collections from N. Sikkim and Yunnan. Scapania schljakovii (Figure 1G,H) is morphologically similar to S. ornithopoides (With.) Waddell (see Note 1. at end of paper). It is distinct from S. ornithopoides in its peculiar leaf areolation with irregularly coarsely thickened cell walls and perianth structure (Figure 1E, I,J; Potemkin 2001: Figure 3: H, J, M, O). Despite Potemkin (2001) pointing out the deeply pigmented marginal leaf cells in type material of S. schljakovii, this character is often only distinct in some leaves. Scapania schljakovii is designated by Potemkin (2002) as the type species of the section Muelleria Potemkin on the basis of its very fleshy cylindrical perianth, arcuately inserted non-decurrent leaves, unusual leaf areolation with sharply defined area of strongly elongated basal cells of ventral lobe and quite peculiar trigones ± concave medially and ± bulging in distal portions (Figure 1D,E,F,I,J; Potemkin 2001: Figure 3: G–P; Potemkin 2002). The section includes also S. himalayica Müll.Frib., which is known without perianths from high locations in Nepal and Sikkim, 3500–3900 m a.s.l., and is considered to be derived from the section Plicaticalyx (Müll.Frib.) Potemkin. Both species occur in the same area of the Himalayas in Abies–Rhododendron communities. Scapania schljakovii shares with S. davidii Potemkin spine formation near the perianth mouth. However, spines in S. schljakovii were recorded on outer perianth surface (Potemkin 2001: Figure 3: H, M) vs. on inner perianth surface in S. davidii (Majumdar et al. 2016: Figures 1: T, 2: Q). Formation of spines near the perianth mouth needs further study when new collections with perianths are available.