Didymocarpus obtusus Wall. ex R.Br.

Didymocarpus obtusus Wall. ex R.Br. View in CoL , Cyrtandreae 118. 1839, nom. illegit. FigS. 1 View Fig & 2 View Fig

Deciduous, perennial, lithophytic herbs, to 30 cm tall. Primary stem stout, cylindrical, 1–4 cm long, terminating in 2–6, opposite, long-petiolate leaves; 1–4 slender stems from apex of primary stem, each terminating in 2 or 4 reduced sessile leaves with a peduncle arising from each axil; stems covered with short appressed acute hairs, long spreading acute hairs and yellow sessile globose glands; petioles 6– 21 cm long, hairy; lamina broadly elliptic, ovate or suborbicular, 5–18 × 4–15 cm, base cordate to cuneate, sometimes oblique, margins crenate to serrate, subacute to obtuse or sometimes rounded at apex, green above, pale green beneath, dotted with yellow sessile globose glands on both surfaces, upper surface pubescent with short acute appressed hairs, lower surface glabrescent with short acute hairs only along the veins; secondary veins 4–8 pairs, slightly impressed above, raised beneath. Inflorescences axillary, corymbose cymes, not overtopping the leaves; peduncles slender, 2–6 cm long, sparsely glandular pilose; pedicels slender, 2–8 mm long, sparsely glandular pilose. Bracts broadly ovate, 3–6 × 2–7 mm, minutely toothed, green, dotted with yellow sessile glands on both surfaces, glandular and eglandular hairy outside, glabrous inside. Calyx campanulate, c. 6 mm long, 5-lobed, purplish, with yellow sessile glands and glandular hairs outside, glabrous inside; tube c. 4 mm long; lobes triangular, 2–3 mm long, acute or obtuse at apex. Corolla funnelform, c. 5 cm long, glandular hairy outside, glabrous inside; tube c. 3 cm long, purplish; limb bilabiate, posterior lip (upper) 2- lobed, rounded, c. 6 × 8 mm, anterior lip (lower) 3- lobed, oblong-rounded, c. 9 × 6 mm, purple or bluish-purple with white striations on throat and lobes. 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. 8 mm long, whitish, sparsely glandular puberulent; anthers oblong, c. 2 mm long, coherent, creamy, bearded with short moniliform hairs, with a brownish patch and a few glandular hairs near connectives; staminodes 3, reduced to minute filaments of unequal length, 2–3 mm long, whitish, glabrous. Disc cupular, c. 2 mm high, minutely lobed, yellow, glabrous. Ovary cylindrical, c. 3 cm long, sessile, whitish-brownish-purple, glabrous; style c. 2 mm long, not clearly demarcated, brownish, glabrous; stigma capitate, whitish, papillose. Capsules linear, slightly falcate, c. 5 × 0.2 cm, brown, glabrous, stipitate, stipe 0.5–1 cm long. Seeds numerous, unappendaged, ellipsoid-oblong, 0.2–0.5 × 0.1–0.2 mm, testa reticulate.

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

Habitat: Grows on mossy rocks in moist tropical and wet montane temperate forests at an elevation ranging from 900 to 2400 m.

Distribution: Bhutan, Nepal, India ( Fig. 3 View Fig ).

Specimens examined: INDIA, Arunachal Pradesh, Tawang district , Jung to Tawang, N 27 ̊34'51.456'', E 91 ̊58'26.148'', 2148 m, 13.09.2019, A. S . Kanthraj 321064; Sera Village way to Lumla, N 27 ̊34'3.36'', E 91 ̊52'10.2'', 2373m, 13.09.2019, A. S . Kanthraj 321065 ( LWG); West Kameng district , Dirang MTB node, Sapper Army Camp, N 27 ̊23'22.632'', E 92 ̊11'43.368'', 1728 m, 07.09.2018, A. S . Kanthraj 319872; Dirang to Sella Pass , 5 km before Nyukmadung War Memorial, N 27 ̊23'37.968'', E 92 ̊9'30.42'', 1836 m, 07.09.2018, A. S . Kanthraj 319873; Mohankem Army Camp , N 27 ̊25'14.16'', E 92 ̊7'27.12'', 2112 m, 07.09.2018, A. S . Kanthraj 319874 ( LWG) .

Notes: When Don (1825) originally described D. cinereus in his ‘ Prodromus Florae Nepalensis ’, he based it on an unnumbered collection attributed to “ Wallich, Nepal ”. Don’s Prodromus was based on specimens from Nepal sent to Aylmer Bourke Lambert (1761–1842) by Francis Buchanan- Hamilton (1762–1829) and Nathaniel Wallich (1786–1854) in 1818 and 1819 ( Stearn, 1945; Weber et al., 2000). Wallich also had suggested several manuscript names for his Nepal specimens distributed to several herbaria, including the Lambert herbarium. Don had adopted some of these Wallichian names, but not all, in his Prodromus . After Lambert’s death in 1842, his herbarium was sold in parts to many European institutions ( Miller, 1970). Wallich’s Nepal plants in Lambert herbarium, including the types of Don’s Prodromus are now in BM, duplicates in LINN (in Smith’s herbarium), now transferred to K, and other material is in BR, P-JU and CGE (Stafleu & Cowan, 1988). Our search for the original material associated with D. cinereus resulted in locating two Wallichian sheets in BM (BM000521817 and BM000948600). Both sheets were part of the Lambert herbarium acquired in 1842 and were determined and stored as D. cinereus in BM (Ranee Prakash, pers. comm.).

The sheet, BM000521817, contains eight fragments, with three flowering specimens mounted in the upper half, and five fragments (in vegetative and flowering stages) in the lower half. The sheet carries the labels, “ INDIA WALLICH” (in print) and “ Didymocarpus obtusa ” (in hand), below the upper row of specimens, and “ Didymocarpus cinerea D.Don ” (in Don’s own handwriting) at the right hand bottom of the lower row of specimens. It seems that the label INDIA, instead of NEPAL, might have been wrongly printed on the sheet. The other sheet (BM000948600) bears eight fragments in flowering and fruiting stages. The label at the lower bottom on the left hand side of the sheet shows: “ Didymocarpus obtusa Wall. , Nepal 1819, Wallich”, and C.B. Clarke’s annotation “ D. cinerea D.Donis same as D. obtusa Wall. ” on the right hand side. Both sheets represent true D. cinereus and match perfectly with Don’s original description. Among the two, BM000521817, which bears Don’s original annotation, is designated here as the lectotype for D. cinereus .

The occurrence of D. cinereus in India has long been disputed. The confusion began with Clarke’s (1874) misinterpretation of some of the Sikkim Himalayan specimens as ‘ D. obtusa DC. ’ [= D. obtusus Wall. ex R.Br. ], now an avowed synonym of D. cinereus . Hilliard and Burtt (1995) segregated the Sikkim Himalayan elements of Clarke (1874) into a new species, D. triplotrichus Hilliard , very closely allied to D. cinereus but distinct from it primarily in the indumentum and floral characters ( Table 1). Mukherjee and Parai (1995), Mukherjee et al. (2008) and Roy (2017) overlooked the above and erroneously reported the occurrence of D. cinereus for the gesneriaceous flora of the eastern Himalaya of India. These reports not only misinterpreted Clarke’s (1874) description and illustration of D. obtusus (now D. triplotrichus Hilliard ) as D. cinereus , but also included an exsiccata of misidentified, misinterpreted or missing specimens. Mukherjee and Parai (1995) and Mukherjee et al. (2008) cited a solitary specimen from Sikkim [Great Rangeet, 1200 m, YHB 974 (CAL)] under D. cinereus . This specimen is not traceable either in CAL (V.P. Prasad, pers. comm.) or any other herbaria.

Roy (2017) included D. cinereus based on two specimens from Jalpaiguri and Darjeeling area of West Bengal: i) Mrs Prabha & Miss Ramola 6343, and ii) G. King s.n. As evident from the herbarium label, the first specimen was collected from Nagarkot, a place in Nepal on 29 August 1966 (CAL, accession number 552006). Another specimen with the same collection number is also available in BM (BM000832926). Both the specimens represent the true D. cinereus . However, Roy (2017) wrongly cited the place of collection of Mrs. Prabha & Miss Ramola 6343 as ‘Nagrakot- Jalpaiguri ( West Bengal)’ and the date of collection as '23.4.14'. Roy (2017) cited the second specimen under D. cinereus with the following collection data: ‘Pankabaree-Darjeeling, 2500 ft, 30.8.1877, G. King s.n. (CAL)’. In CAL there is no such specimen of G. King s. n. collected in 1877. King’s specimen that matches with the collection data given in Roy (2017) is G. King 4043 (CAL, accession number 332123), which shows short petiolate leaves not overtopping the inflorescence, and belongs to D. triplotrichus , but not D. cinereus . Nevertheless, Roy (2017) misidentified G. King 4043 and included it under D. andersonii C.B.Clarke , a species distinguishable from D. triplotrichus and D. cinereus by its purplish connate bracts concealing the pedicels and shorter sessile capsules with an acute tip. Moreover, Roy (2017) reproduced Clarke’s (1874) illustration (t. 61) under D. cinereus , which also indicated that she was probably confused with the actual identities of D. triplotrichus and D. cinereus . Interestingly, Sinha and Datta (2016) did not include D. cinereus in their taxonomic account on the Gesneriaceae of North East India. D. cinereus thus remained elusive until this new report of the species from the Eastern Himalaya of India.