Plagiothecium filifolium G.J.Wolski, 2023

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

Plagiothecium filifolium G.J.Wolski sp. nov.

Type.

Pakistan, Mt. Nanga Parbat , Mazeno Base Camp, 4000 m alt, on boulder, 15 September 1990, M. Higuchi 20479, holotype LOD 15018 , isotype PMNH .

Description.

Plants green-yellow, without metallic luster; stems complanate-foliate, 1.0-1.5 cm long; cross-section rounded, with a diameter of 200-300 μm, the central strand well developed, epidermal cells 9-13 × 11-15 (M 11 × 13) μm, the parenchyma thin-walled, 15-21 × 16-28 (M 18 × 22) μm; leaves folded, most strongly in the upper part of leaves, concave, asymmetrical, those leaves from the middle of the stem 1.6-2.2 × 0.5-0.8 (M 1.9 × 0.66) mm; leaves gradually tapering to long, acuminate, not denticulate apex; costae two, very thin and delicate, extending up to 1/2 of the leaf length, reaching 140-423 (M 282) μm; laminal cells rather symmetrical, the length and width very variable, but dependent on location: 97-160 × 7-10 (M 127 × 8) μm at apex, 105-180 × 7-9 (M 150 × 8) μm at mid-leaf and 70-165 × 8-11 (M 118 × 9) μm towards insertion, cell areolation tight; decurrency short, 220-530 μm, composed of 3 rows of gently inflated, rectangular cells, 47-147 × 12-21 (M 97 × 16) μm. Sporophytes unknown so far (Fig. 5 ). In these studies, Plagiothecium filifolium (M. Higuchi 20479) has been recorded on boulders.

Etymology.

Filum- [Lat.] thread; -folium [Lat.] leaf. The present species is named in reference to the most distinctive feature - its threadlike leaf apex.

Figures

Figure 5. The most important taxonomic features of Plagiothecium filifolium A, B leaf shape C leaf apex D folding of the apex E, F dimension of cells (E from the middle F basal part of the leaf) (from M. Higuchi 20479).