Plagiothecium cordatum G.J.Wolski, 2024

Wolski, Grzegorz J., Latoszewski, Mikolaj, Cargill, D. Christine & Buck, William R., 2024, Re-assessment of type material of Plagiothecium novae-seelandiae Broth. and descriptions of four new Plagiothecium taxa (Bryophyta, Plagiotheciaceae) from Australasia, PhytoKeys 238, pp. 95-117 : 95

Plagiothecium cordatum G.J.Wolski sp. nov.

Type.

Holotype: New Zealand, Boundary Creek , McKerrow Range, ca 4000 alt., leg. Colin D. Meurk, 17 Jan. 1974 (CHR538916!) .

Description.

Plants small, ascending and julaceous, yellow to yellow-green, with metallic luster, forming dense mats; stems 1.0-2.0 cm long, in cross-section rounded, with a diameter of 220-240 μm, the central strand well-developed, epidermal cells thick-walled, the parenchyma thin-walled; leaves symmetrical, lanceolate, concave, longitudinally folded, imbricate, closely arranged on the stem, those leaves from the middle of stem 1.7-2.0 mm long and the width measured at the widest point 0.7-0.9 mm; the apex acuminate, entire, not denticulate; leaf base cordate-rounded; costae two, weak and thin, extending usually to ½ of leaf length; laminal cells asymmetrical, the length and width variable but dependent on location: 140-165 × 5-7 μm at the apex, 135-160 × 5-7.5 μm at midleaf, 65-100 × 10 μm toward insertion; due to cell width, cell areolation very narrow; decurrency of 3-4 rows of rectangular cells, forming narrow, wedge-shaped auricles, 300 μm long (Fig. 7 ); sporophytes so far unknown; sexual condition unknown.

Plagiothecium cordatum so far has been recorded from New Zealand, McKerrow Range, Boundary Creek (CHR538916), South Island, Fiordland National Park, Corland Burn, South Branch, 2 km north of Mount Burns (AK352034) and from Macquarie Island, Sawyer Creek (HO610227) (Fig. 7 ). This species was noted on the south side of southernmost waterfall, on undercut bank at edge of creek (HO610227), on Nothofagus menziesii forest epiphytic on trunk of silver beech (AK352034).

Etymology.

The name of this taxon - Plagiothecium cordatum refers to the heart-shaped (Latin: cor - heart) base of leaves of this species.

Figures

Figure 7. Selected taxonomic features of Plagiothecium cordatum A, B shape and dimensions of leaves C leaf apex D dimensions and shape of cells from middle part of the leaf (from the type of material of P. cordatum CHR 538916!, photo. G. J. Wolski, November 12, 2022).