Hook.f. & Thomson
Description
Begonia cathcartii is a perennial herb of the moist eastern Himalaya and neighbouring montane Southeast Asia, recorded from northern India (Sikkim, Darjeeling), Nepal, Bhutan, Myanmar, Thailand and Peninsular Malaysia; GBIF documents about 138 occurrences. It is a plant of shaded, humid broadleaved forest, growing on damp banks, mossy boulders and stream sides where humidity remains high, chiefly between about 1500 and 2700 m. The photographed material came from the Darjeeling hills at Utaray near 2100 m and from Yoksam in Sikkim at about 1950 m, both in April, matching the cool, dripping understorey it favours during the pre-monsoon flush.
The plant is a fleshy, somewhat succulent herb with an erect or ascending, sparingly branched stem arising from a rhizomatous or tuberous base. As in the genus the leaves are alternate, markedly asymmetric (oblique) at the base, broadly ovate, acuminate, with a toothed and often shallowly lobed margin and conspicuous stipules. The flowers are monoecious and borne in axillary cymes, white to pale pink; the staminate flowers bear several stamens while the pistillate flowers sit above a winged inferior ovary. The fruit is a three-winged capsule, with one wing usually larger, releasing very numerous minute seeds.
Begonia (Begoniaceae) is one of the largest angiosperm genera, and B. cathcartii belongs to its rich Sino-Himalayan rhizomatous assemblage, named for J. F. Cathcart. Its monoecious flowers, unequal capsule wings and asymmetric leaves are characteristic of the family. Dependent on humid forest microhabitats, it is locally frequent and not formally assessed as threatened, but sensitive to forest clearance and desiccation.
Author: Hook.f. & Thomson · Sources: POWO (Kew), GBIF, Flora of China Vol. 13, Flora of Bhutan Vol. 2, Flora of Nepal, Flora of Pakistan, Hooker Begonias of the Himalaya in Flora of British India