Hypnodontopsis spathulata H. Akiyama & At. Tanaka, Bryol. Res.

Chantanaorrapint, Sahut, Sevanakun, Nilobon, Suwanmala, Orawanya, Sukkharak, Phiangphak, Printarakul, Narin & He, Si, 2021, The moss family Rhachitheciaceae (Dicranales, Bryophyta) in Thailand, Phytotaxa 520 (3), pp. 279-284 : 280

Hypnodontopsis spathulata H. Akiyama & At. Tanaka, Bryol. Res. 8(5): 134. 2002. ( Fig. 1 )

Type: — MYANMAR. Chin State, Murata et al. 22245 (holotype: HYO, isotypes: CONN, HIRU) .

Plants up to 3 mm high (including sporophytes), light green to yellowish green, forming loose turfs. Rhizoids colorless to reddish, clustered at stem base. Stems erect, simple, in cross section 4–6 layers of cells across, 90–120 µm in diameter, epidermal cells in 1 layer, thin walled; medullary cells larger in size, thin walled; central strand not differentiated. Axillary hairs uniseriate, consisting of 2–4 cells vertically, 125–175 µm long, colorless. Leaves appressed when dry, erect to spreading when moist, oblong to spathulate, 0.8–0.9(–1.1) × 0.25–0.45 mm; apex shortly acuminate; margins plane, entire to slightly crenulate with papillae, elimbate; costa stout, ending below leaf apex, smooth on both surfaces, in cross section at mid-leaf with single layer of large, thin-walled cells on adaxial and 2 layers of thick-walled cells on abaxial; upper laminal cells rounded, 5–12 µm in diameter, chlorophyllose, thick-walled, with 2–5 papillae on both surfaces; lower laminal cells hyaline, quadrate to rectangular, 15–100 × 7.5–15 µm, thin-walled, smooth, occupying 1/4–1/3 the leaf length. Asexual reproduction by fusiform gemmae, occurring on the adaxial surface of leaf; gemmae dark green to brown, consisting of 8–16 cells.

Dioicous. Perigonia not seen. Perichaetia terminal, perichaetial leaves light green, oblong to elliptic, 1–1.2 mm × 0.3–0.5 mm, apex acuminate, base convolute-sheathing. Seta yellowish green, 0.5–0.6 mm long, smooth, spiraling in both wet and dry conditions. Capsule light green to dark green, ovoid, ca. 0.6 mm long, 0.35 mm in diameter, with deeply 8-ribbed urns, shortly exerted above the leaves; exothecial cells at mouth dark red or reddish brown, quadrate to subquadrate, moderately thick-walled, cells below pale brown, variable in size, quadrate to hexagonal, 32–60 × 10–20 µm, moderately thin-walled, without stoma. Operculum small, flat, ca. 150 µm in diameter. Peristome single, 16 teeth fused into 8 pairs, yellowish orange, lanceolate to linear-lanceolate, with palisade-like markings on both surfaces, inserted ca. 1/2 within the mouth. Spores pale brown, globular, smooth, 25–32 µm in diameter. Calyptra not seen.

Habitat and ecology: —In Thailand, populations of Hypnodontopsis spathulata were found growing on tree trunks in lower mountain pine-oak forests, between 1200 and 1500 m.

Distribution: — Myanmar (Chin State) ( Akiyama & Tanaka 2002). New for Thailand (Chiang Mai).

Specimens examined: — THAILAND. Chiang Mai: Chiang Dao Wildlife Sanctuary , 1200–1500 m, 19 o 21’ 22.87”N, 098 o 50’ 02.19”E, 15 June 2018, N. Sevanakun 296 ( BKF, PSU) ; 13 August 2018, N. Sevanakun 297 ( BKF, PSU) , 15 August 2018, N. Sevanakun 298 ( BKF, PSU) .

Notes: — Hypnodontopsis spathulata is morphologically closest to H. apiculata Iwatzuki & Noguchi (in Iwatsuki 1957: 304). A detailed discussion about the differences between the two species has been given in Akiyama & Tanaka (2002).

Hypnodontopsis spathulata was previously known only from the type specimen. The new discovery in Thailand represents the second record of H. spathulata . The species might have been easily overlooked in the field by previous botanical explorations because of its small size. In Thailand, it is presently known only from Chiang Dao Wildlife Sanctuary (about 1000 km from the type locality), but it might have a wider distribution and may also occur in other areas of northern Thailand and southwestern China.

Figures

FIGURE 1. Hypnodontopsis spathulata H. Akiyama & At. Tanaka.: A. Gametophyte with sporophyte. B. Stem in cross section. C. Axillary hairs. D–F. Leaves. G–H. Leaf apices. I. Cross section of leaf at mid-leaf. J. Upper laminal cells. K. Lower laminal cells. L. Propagules. M–N. Perichaetial leaves. O. Sporophyte. P–Q. Peristome teeth. R. Spores. Drawn by N. Sevanakun, all from N. Sevanakun 296 (PSU).