Plagiothecium denticulatum var. obtusifolium (Turner) Moore, 1873

Wolski, Grzegorz J., Khan, Aamir Shehzad & Paszko, Beata, 2023, New taxa of Plagiothecium (Plagiotheciaceae) from Pakistan, PhytoKeys 236, pp. 1-16 : 1

Plagiothecium denticulatum var. obtusifolium (Turner) Moore

Plagiothecium denticulatum var. obtusifolium (Turner) Moore, Proceedings of the Royal Irish Academy 1: 424 (1873).

≡ Hypnum denticulatum var. obtusifolium Turner, Muscologiae Hibernicae Spicilegium 146, T. 12, f. 2 (1804).

≡ Plagiothecium obtusifolium (Turner) J.J.Amann, Mémoire de la Société Vaudoise des Sciences Naturelles 3: 61 (1928). Holotype: fig. 2, tabela 12 "T. 12, f. 2" (Turner 1804: 237) (fig. 3). Epitype (selected by Wolski et al. 2022) [Ireland], in summo montis Bulbein jugo, ab oculatissimo D. Brown lectam, benigne communicavit D. Templeton, BM000890810! (fig. 10).

= Plagiothecium sandbergii Renauld & Cardot, Contributions from the United States National Herbarium, 3: 274 (1895), Lectotype (selected by Wolski et al. 2022): U.S.A., Idaho, Kootenai County, Hope, J.H. Sandberg, D.T. Macdougal, A.A. Heller 1174, August 1892 (PC0132604!); isolectotypes: NY507114!, available online; US70396!, available online; FH220148. Additional original material from locus classicus (not signed "No. 1174"): 456 NY507115!, available online. Additional Sandberg material, potentially from locus 457 classicus: PC0132605! Additional Sandberg material: FH220147.

= Plagiothecium denticulatum var. auritum Kern, Jahresbericht der Schlesischen Gesellschaft für Vaterländische Cultur 91(Abt. 2b): 97 (1914). Lectotype (selected by Wolski et al. 2022): [Italy] South Tirol, Ortler, Martelltal, in Felshöhlungen oberhalb der Cevedalehütte, F. Kern s.n., 2350 m, 30 July 1913, herb. I. Thériot (PC0132639!).

Description.

Plants light green, with metallic luster; stem in cross section rounded, 150-200 μm in diameter; the central strand well developed, epidermal cells 12-20 × 15-31 (M 16 × 23) μm, the parenchyma thin-walled, 25-43 × 21-39 (M 34 × 30) μm; leaves very concave, not folded, julaceous, elliptical-ovate, very slightly asymmetrical, 1.6-1.7 × 0.8-0.95 (M 1.65 × 0.87) mm; the apex obtusely-apiculate; costae two, extending usually up to 1/3 or ½ of the leaf length, ranging 250-530 (M 390) μm; cell areolation loose; length and width of cells very variable, but dependent on location: 85-140 × 15-18 (M 113 × 17) μm at the apex; 95-170 × 12-18 (M 133 × 15) μm at midleaf; 98-200 × 15-25 (M 150 × 20) μm toward insertion; broad decurrency 260-400 (M 330) μm; alar cells rounded-rectangular, 51-98 × 21-31 (M 75 × 26) μm; sporophytes not found in this material (Fig. 2 ). In these studies, Plagiothecium denticulatum var. obtusifolium (M. Higuchi 20499) has been recorded on soil.

The next two samples (M. Higuchi 20460 and M. Higuchi 20479) were characterized by a unique combination of qualitative and quantitative features of their gametophytes. They did not match any of the taxa of the genus currently known in the Northern and Southern Hemispheres.

The specimen collected by M. Higuchi (M. Higuchi 20460) represents two morphotypes that are microscopically very different from each other. This material differs in the length and width of the leaf, the shape of the apex, the length and width of the cells of the top, middle and basal part of the leaf - which are one of the most important taxonomic features for the whole genus. In addition, the result of the U Mann-Whitney test showed that the length and width of the cells of individual parts of the leaf of these morphotypes differ statistically significantly (p<0.001) from each other. Thus, it was proposed to recognise two varieties - Plagiothecium higuchii var. higuchii and P. higuchii var. brevicellum .

Figures

Figure 2. The most important taxonomic features of Plagiothecium denticulatum var. obtusifolium A leaf shape B-D dimension of cells (B from the apex C the middle D basal part of the leaf) E decurrent cells (from M. Higuchi 20499).