Henckelia khasiana, a new species of Gesneriaceae from India

A new species of Henckelia (Gesneriaceae) is here described and illustrated. It is morphologically most similar to H. oblongifolia but differs in having lanceolate calyx lobes, two prominent longitudinal flaps on the inner surface of the corolla tube, bilobed stigma and tomentose capsules. A detailed description of the new species with colour photographs, affinities and a comparison with related species is given. Based on the present data, the new species is provisionally assessed as Critically Endangered (CR) according to IUCN Red List Categories and Criteria.

The authors while revising the taxonomy of the family Gesneriaceae in India, came across some interesting specimens of Henckelia from Mawsynram in East Khasi Hills district of Meghalaya. Critical examination of the specimens at various herbaria (ARUN, ASSAM, BM, CALI, E, K) and the study of relevant literature revealed that they were morphologically close to H. oblongifolia (Roxb.) D.J. Middleton & Mich.Möller in having caulescent habit, axillary inflorescence with dichotomously branching peduncles, persistent calyx and corolla with yellow lines on the throat; but they also differed in other characters related to the nature and pubescence of leaves, calyx and corolla, fusion of anthers, structure and colour of staminodes, shape of stigma, among others. Differences that will be discussed below led us to describe, on the basis of the mentioned specimens, a new species.

MATERIALS AND METHODS
The new species is described on the basis of field observations and the examination specimens of Henckelia collected in India, including types at ARUN, ASSAM, BM, CAL, CALI, E, K, MA (acronyms following Thiers, 2020 continuously updated). Herbarium specimens were prepared following the procedure by Forman & Bridson (1989). Specimen images and species names were all checked from JSTOR Global Plants (http://plants.jstor. org), Tropicos (http://www.tropicos.org) and the International Plant Names Index (http://www.ipni.org). Pro-tologues and relevant literature were examined and the description was prepared following Stearn (1992). Photographs of the plants in the field were taken with an α-55 DSLR Camera (Sony, Japan) and those of floral parts with a stemi 508 stereomicroscope (Zeiss, Germany) attached to an Axiocam 105 colour camera. A distribution map was created using the maps from d-maps.com (https://d-maps. com/index.php?lang=en). The provisional conservation threat assessment followed IUCN Categories and Criteria (IUCN 2019). It is similar to Henckelia oblongifolia (Roxb.) D.J.Middleton & Mich.Möller because of its general appearance, flower colour and yellow lines on the corolla throat, but differs in the shape of the calyx lobes (lanceolate vs. deltoid), the corolla tube (two prominent longitudinal flaps on the inner side vs. without longitudinal flaps), the stigma (bilobed vs. obdeltoid) and capsules (tomentose vs. pubescent).
Distribution and habitat. -Hitherto known only from the type locality (Fig. 2) in tropical evergreen forest at altitudes around 1300 m. It was found in relatively damp, shady areas along rivulets with dense understory.
Phenology. -Flowering and fruiting from September to November.
Etymology. -The specific epithet is derived from the floristically rich Khasi hills in Meghalaya, where the type locality Mawsynram is situated.
Conservation status. -Henckelia khasiana sp. nov. is known only from a single location in the type locality Mawsynram in East Khasi Hills district of Meghalaya. The area of occupancy is assumed to be less than 10 km 2 . It is under severe threat due to the expansion of highways and other developmental activities in the area. Further surveys in other likely areas are required to estimate the conservation status of the new species. Based on the available data, it is provisionally assessed as "Critically Endangered" (CR) according to the criteria B2ab(iii) of IUCN Red List Categories and Criteria (IUCN 2019).
Notes. -Among the species of Henckelia occurring in India, H. khasiana is most similar to H. oblongifolia but differs from the latter in several characters summarized in the diagnosis above and in Table 1.