Lam.
Description
Lobelia nummularia is a creeping, mat-forming perennial herb of the Campanulaceae (subfamily Lobelioideae), widely distributed across tropical and subtropical Asia. GBIF data (over 2,600 occurrences) confirm a broad native range spanning the eastern Himalaya, southern China, Taiwan, Indochina, the Malesian region and Papua New Guinea, with naturalised or cultivated records further afield. The species favours shaded, humid forest floors, mossy banks, ravine sides and the margins of streams in evergreen broadleaved and subtropical montane forest. The collection from the Ruigi-Chu valley in West Bengal at 2,100 m in May illustrates its habit of carpeting damp, sheltered ground in the lower montane belt.
The slender, prostrate stems root at the nodes and form extensive mats. Leaves are alternate, small, orbicular to broadly ovate or cordate, shortly petiolate, with shallowly crenate to serrate margins, the rounded coin-like blades giving rise to the epithet nummularia. The solitary axillary flowers are borne on long, filiform pedicels. The corolla is bilabiate, pale purplish-pink to whitish, with the two upper lobes erect and the three lower lobes spreading; the five anthers are fused into a tube around the style. The fruit is a small, more or less globose to subglobose capsule containing numerous minute seeds.
Members of subfamily Lobelioideae are characterised by their resupinate, strongly zygomorphic flowers and connate anthers, and like many lobelias the species contains piperidine alkaloids. As a ground-cover element of intact understorey, L. nummularia contributes to soil stabilisation on humid forest banks. Its very wide distribution renders it secure overall, though forest clearance threatens local populations dependent on continuous shade and humidity.
Author: Lam. · Sources: POWO (Kew), Flora of China Vol. 19, Flora of Bhutan Vol. 2, GBIF, Lammers: World Checklist and Bibliography of Campanulaceae (2007)