Didymocarpus obtusus

Didymocarpus obtusus View in CoL auct., non [Wall. ex] R.Br.; C.B.Clarke, Commelyn. Cyrtandr. Bengal. 91, t. 61. 1874. Fig. 4 View Fig

Deciduous, perennial, lithophytic herbs, to 20 cm tall. Primary stem stout, cylindrical, 1–2 cm long, terminating in 2 opposite petiolate leaves; 1 slender stem from apex of primary stem, terminating in 1 or 2 pair of sessile leaves with a peduncle arising from each axil; stems covered with short appressed acute and long acute patent hairs and yellow sessile globose glands; petioles 2–8 cm long, hairy; lamina broadly ovate to suborbicular, 4–16 × 3–11 cm, base cordate to cuneate, sometimes slightly oblique, margins crenate to serrate, obtuse to rounded at apex, green above, pale green beneath, dotted with yellow sessile globose glands on both surfaces, upper surface with short acute appressed and longer acute patent hairs, lower surface glabrescent with short acute and long spreading hairs only along veins; secondary veins 4–8 pairs, slightly impressed above, raised beneath. Inflorescences axillary, corymbose cymes, overtopping the leaves; peduncles slender, 4–10 cm long, sparsely glandular pilose; pedicels slender, 4–15 mm long, sparsely glandular pilose.

Bracts broadly ovate, 3–6 × 4–7 mm, green, strigose, dotted with yellow sessile glands on both surfaces, eglandular and glandular hairy outside, glabrous inside. Calyx campanulate, 4–6 mm long, 5-lobed, purplish-brown often with green tinge, sparsely glandular hairy with yellow sessile globose glands outside, glabrous inside; tube c. 4 mm long; lobes triangular, c. 1.5 mm long, subacute to obtuse. Corolla c. 5 cm long, funnelform, purple, glabrous; tube c. 3 cm long; limb bilabiate, posterior lip (upper) 2-lobed, rounded, c. 6 × 8 mm, anterior lip (lower) 3-lobed, ovate-rounded, c. 8 × 10 mm, without prominent striations on lobes, with mild white striations on the throat. Fertile stamens 2, inserted above the middle of corolla tube, enantiostylous, stamens and style deflected reciprocally towards left or right side away from each other; filaments slender, c. 1 cm long, whitish, glabrous; anthers oblong, c. 3 mm long, coherent, creamy, glabrous, with a brownish patch and a few glandular hairs near connectives; staminodes 3, reduced to minute filaments of unequal length, c. 3 mm long, whitish, glabrous. Disc cupular, c. 1 mm high, pale green, glabrous. Ovary cylindrical, slightly narrowed towards base, c. 25 × 1 mm, green, glabrous; style c. 2 mm long, green, glabrous; stigma capitate, concave, whitish, papillose. Capsules linear, erect, c. 5 × 0.2 cm, brown, glabrous, stipitate, stipe 1–1.5 cm long. Seeds numerous, unappendaged, ellipsoid-oblong, 0.2–0.4 × 0.1–0.2 mm, testa reticulate.

Flowering & fruiting: Flowering from July to September and fruiting from August to October.

Habitat: Grows on moist mossy rocks on mountain slopes in tropical moist deciduous forests between 950 and 1065 m elevation.

Distribution: India (Eastern Himalaya), endemic ( Fig. 3 View Fig ).

Specimens examined: INDIA, West Bengal, Darjeeling district, above Pankhabari, 2500 ft, 30.08.1877, G. King 4043 ( CAL [Acc. no. 332123]); Between Kurseong and Pankhabari , 30.08.1857, T. Thomson s.n. ( CAL [Acc. no. 332130]); Makaibari to Pankhabari Road , 1 km after Makaibari , N 26 ̊51'8.28'', E 88 ̊15'33.12'', 1065 m, 11.08.2018, A. S. Kanthraj 319846; Makaibari to Pankhabari Road, 3 km before Pankhabari, N 26 ̊50'57.48'', E 88 ̊15'47.16'', 950 m, 11.08.2018, A. S. Kanthraj 319847 ( LWG); Pankhabari, 10.1868, S. Kurz s.n. ( CAL [Acc. no. 332131]); Pankhabari, 2500 ft, s.d., s.coll. s.n. ( CAL [Acc. no. 332121]); s.loc., 1878, G. King s.n. ( CAL [Acc. nos. 332125, 332126]); s.loc., s.d., s.coll. s.n. ( CAL [Acc. nos. 332132, 332133]) .

Notes: Hilliard and Burtt (1995) originally described D. triplotrichus , based on specimens collected by J.S. Gamble from Pankhabari in Darjeeling of West Bengal state (previously in Sikkim) in August 1880. Besides the types, seven more sheets of D. triplotrichus were located in CAL. Of these, four sheets contained specimens collected in and around Pankhabari, by Thomas Thomson in 1857, Wilhelm Sulpiz Kurz in 1868, George King in 1877 & 1878, and the fifth one by an unknown collector without collection date. These were earlier identified and stored as ‘ D. obtusa Wallich’. The remaining two sheets in CAL (determined wrongly as ‘ D. cinerea D.Don’ by K. Biswas in 1937) are without any information on the locality, collector, and date of collection.

Didymocarpus triplotrichus View in CoL is hitherto represented only from the types and the few older specimens in CAL. Other than the protologue and a brief description provided by Hilliard (2001) in Flora of Bhutan (with reference to Darjeeling material only), D. triplotrichus View in CoL has not been dealt with finer details in any taxonomic treatises. The report of D. triplotrichus View in CoL by Sinha and Datta (2016) is ambiguous as the sole specimen cited by them, N. R. Mondal & P. Singh 13484 (BHSC) collected in Sikkim, East District, Machong, Rikep, Barapathling on 7 July 1991, actually represents D. andersonii View in CoL . Interestingly, they cited the same specimen under D. andersonii View in CoL . Roy (2017) also wrongly included N. R. Mondal & P. Singh 13484 (BHSC) under D. triplotrichus View in CoL .

During a field survey conducted in Darjeeling Himalaya in August 2018, one of the authors ( KAS) collected D. triplotrichus View in CoL from Pankhabari. The present collections, made at two locations along the Pankhabari road at 950–1065 m elevation range, represented a recollection of this narrow endemic species 138 years after the type collections .

Didymocarpus triplotrichus is characterized by the presence of three types of hair on the plant, i.e., short acute, long spreading and glandular hairs. The species exhibits reciprocal enantiostyly, where the style and stamens are deflected to the left or right in opposite directions. Like in the closely allied D. cinereus , monomorphic enantiostyly is observed in D. triplotrichus , in which both left- and right-styled flowers are found in the same inflorescence of a plant. This species was found in small populations represented by about 20 mature individuals. It faces a high risk of becoming extinct and therefore needs urgent threat status assessment and conservation measures.