53. Lasianthus roosianus Zhu (2002:576). Type: ― THAILAND. Lampang, Muang Pan district, Jae Sawn National Park, 24 June 1996, J. F. Maxwell 96-879 (holotype L0310524!; isotypes BKF!, CMUB!). T hailand: ―Only known from the type collection. Distribution: ―Endemic to Thailand (Northern). Ecology: ―Evergreen forest, growing on granite bedrock at an elevation of 900 m. Flowering and fruiting in June. Notes: ―In Thailand, Lasianthus roosianus seems closely related to L. hookeri but it differs by having leaves lanceolate-elliptic (not oblong), 17‒19 × 3‒4.5 (not 12‒24 × 3‒6) cm, leaf blade chartaceous (not chartaceous or subcoriaceous), adaxially glabrous, abaxially brown-tomentose (not puberulous), calyx campanulate, brown-tomentose (not subglabrous or puberulous), drupes subglobose, brown-tomentose (not subglabrous or puberulent), pyrenes 6 (not 5). Although the specimens of L. roosianus in the Thai herbaria were rather difficult to discover and although we did not find this species in the field, we maintain this species based on the morphological characters mentioned in the protologue. It is also an accepted name in the World Checklist of Selected Plant Families (http://wcsp.science.kew. org/).

Published as part of Napiroon, Tiwtawat, Chayamarit, Kongkanda, Dawson, Sally, Till, Walter & Balslev, Henrik, 2020, A synopsis of Lasianthus (Lasiantheae, Rubiaceae) in Thailand and two additional new species, pp. 1-38 in Phytotaxa 439 (1) on page 28, DOI: 10.11646/phytotaxa.439.1.1, http://zenodo.org/record/13873503