Phaeoceros himalayensis Bapna & G. G. Vyas, J. Hattori Bot. Lab.

Phaeoceros himalayensis (Kashyap) Prosk. ex Bapna & G.G.Vyas, J. Hattori Bot. Lab. 25: 88. 1962. (Figs. 1 & 2)

Basionym: Anthoceros himalayensis Kashyap, New Phytol. 14: 8. 1915.

Type:— INDIA. Western Himalayas, Mussoorie, Kashyap’s illustration (Lectotype: New Phytologist 14: 8. fig 4.4. 1915, designated here).

Thallus yellowish-green to bright green in fresh material, dull green to blackish brown in dry material, prostrate or moderately adhering to the substratum, solid, ecostate, obcordate to fan-shaped, 8–16 mm long, 4–10 mm wide at apex, irregularly branched, with a smooth dorsal surface; apex lobulate to dissected, often attenuate with apical and marginal tubers; dorsal epidermal cells subquadrate, rectangular, or irregularly hexagonal, 60–110 × 30–50 μm, with a solitary chloroplast; pyrenoid present. Rhizoids scattered along the median part of the ventral surface, hyaline to pale brown. Nostoc colonies irregularly scattered on the ventral side of thallus, appearing as dark dots.

Dioicous or monoicous. Androecia scattered, antheridia not seen. Involucres solitary, oblique to erect, cylindrical, up to 3 mm high, smooth or slightly plicate. Capsules up to 12 mm long, 0.4–0.6 mm in diameter, opening longitudinally along 2 suture lines, sutures bordered by 2 rows of thick-walled and dark brown cells, bivalves becoming twisted with drying; epidermal cells of capsule elongate-rectangular, 80–190 × 15–20 μm, walls becoming thickened with maturity, stomata present; assimilative layer 4–5 cell layers in transverse section; the innermost capsule wall cells dark brown, subquadrate to rectangular 25–75 × 25–40 μm; columella well-developed, consisting of 5–10 cells in transverse section. Spores yellowish-brown, rounded-tetrahedral equatorial diameter 30–37.5 μm; proximal face with a distinct trilete mark, each facet concave, the surface finely vermiculate, with a central hollow sparsely surrounded by verrucose projections (Figs. 2A & C); distal face with irregular verrucose projections, sometimes with aggregation in centre (Figs. 2B & D). Pseudoelaters yellowish-brown at maturity, thin-walled, linear or branched, 45–85 μm long, 10–14 μm wide, without helicoidal band.

Habitat and ecology:—The lectotype was found growing with other bryophytes, including Bryum spp. and Fissidens spp. In Thailand, P. himalayensis occurs on moist soil in grassland or dry deciduous forests at altitudes between 1600 and 2150 m. It may grow associated with other hornworts such as Anthoceros erectus Kashyap (1915: 9), and Phaeoceros perpusillus Chantanaorrapint (2009: 30).

Distribution:— India (Kashyap 1915; Asthana & Srivastava 1991), new to Thailand.

Additional specimens examined:— INDIA. Western Himalayas, Mussoorie, in terra et ad rupes, nunc hygrophila, nunc xerophila, subphotophila, ca 2000 m, September 1930, R. S. Chopra s.n. (M-0047283, SING). THAILAND. Chiang Mai: Doi Chiang Dao Wildlife Sanctuary, on soil along walking tail, 19°23’56.3’’ N, 098°52’86.0’’ E, ca 1800 m, 18 December 2011, Chantanaorrapint 2525 C (PSU); Doi Luang Chiang Dao, 19°23’46.09’’ N, 098°53’26.03’’ E, 2150 m, 2 November 2013, Chantanaorrapint & Promma 3123, 3126 (PSU); 3 November 2013, Chantanaorrapint & Promma 3215 A (PSU). The species is currently known only from India and Thailand, but collecting elsewhere may reveal a more widespread distribution.

Taxonomic notes:— Phaeoceros himalayensis is characterized by 1) the presence of tubers at the apical regions of the thallus lobes; 2) the proximal facets of the spore with a central hollow; 3) the distal face of the spore with irregular verrucose projections; 4) the innermost capsule wall cells dark brown, subquadrate to rectangular; and 5) pale to dark brown pseudoelaters. This species may be confused with P. kashyapii Asthana & Srivastava (1991:129) because of the similar gametophyte morphology, however Phaeoceros himalayensis, differs from P. kashyapii by the presence of a central hollow on each proximal face and lamellate projections over distal face.