Clinacanthus Nees (1847: 511)

Bongcheewin, Bhanubong, Darbyshire, Iain, Satitpatipan, Veena & Kongsawadworakul, Panida, 2019, Taxonomic revision of Clinacanthus (Acanthaceae) in Thailand, Phytotaxa 391 (4), pp. 253-263 : 254

Clinacanthus Nees (1847: 511) . Type:— Clinacanthus burmanni Nees (= C. nutans (Burman) Lindau ).

Climbing shrubs; stems quadrangular. Leaves simple, opposite, petiolate. Inflorescences terminal, racemose; peduncles glabrous or pubescent; bracts and bracteoles present, shorter than calyx. Calyx obconical, 5-veined; deeply 5-lobed, lobes equal. Corolla 2-lipped, reddish orange, tubular-obconical or tubular; tube gradually inflated to throat and ± geniculate; rugula absent. Stamens 2, exserted; anthers dorsifixed, monothecous; filaments fleshy; staminodes absent. Pollen prolate, 3-colporate and 6-pseudocolpate or rarely 4-colporate and 8-pseudocolpate, with bireticulate interapertural sculpturing (fide Raj 1973, Daniel et al. 2008). Ovary superior. Disk present. Style persistent. Stigma bifid. Capsules not seen.

Four (or possibly three) species: distributed in Cambodia, China (Guangdong, Guangxi, Hainan, Yunnan), Indonesia (Java), Laos, Malaysia ( Malacca), Vietnam and Thailand. Two species found in Thailand. We elevate C. burmanni Nees var. robinsoni Benoist (1936: 130) from Vietnam to full species status for the first time here. The fourth species, Clinacanthus spirei Benoist (1936: 131) from Laos might possibly be a synonym of C. nutans based on the description from Benoist’s protologue, but the type at P herbarium has not been seen and is not available on the online herbarium catalogue.