Taxonomic studies in the family Asclepiadaceae
1. The taxonomic history and currently accepted classification of the family Asclepiadaceae is presented and discussed. The evolutionary relationship with nearest families, overall geographical distribution and a brief note on economic importance of asclepiads are provided in a general account of the family. 2. A complete taxonomic account of the family for the Flora of Bangladesh is prepared for the first time after a comprehensive survey of the existing taxa. 56 species and 4 varieties from 25 genera are recognized from the area. A dichotomous key to the genera, based on field characters, is provided, and suprageneric, infrageneric and infraspecific classifications are given. A nomenclatural and typification note is provided with a proposal for 16 lectotypes and 3 topotypes according to ICBN. A few nomenclatural changes in some species are made and a full attention is paid to synonymy which results in a number of reductions. Wallich's asclepiad material from Bangladesh held at K-W and other major herbaria have been examined critically, and an index has been prepared with nomenclatural notes and current taxonomic status. There are 7 species and 2 varieties recorded new to the flora of Bangladesh. 2 new varieties, Gymnema acuminatum var. glabrum and Tylophora indica var. intermedia, have been described from Bangladesh. Some investigations on pollinaria, seed morphology and leaf flavonoids have been done. A comparative account of the morphology of the pollinaria of 50 species from 25 genera is prepared with a dichotomous key for the Flora of Bangladesh. Seed morphology under SEM for 14 species from 11 genera provides diagnostic features which may prove useful for supra- and infra-generic classifications. Flavonoid distribution in asclepiads is not taxonomically useful at any level of the taxonomic hierarchy. 3. Two genera, Calotropis and Pentasacme, have been revised for the first time with notes on their taxonomic history, distribution, ecology and synonymy. 3 species of Calotropis and 4 in Pentasacme are recognized. C. procera ssp. hamiltonii (Wight) Ali is reduced to C. procera (Aiton) R. Br. Two sections in the genus Pentasacme are recognized: sect. Pentasacme and sect. Wallichiana (sect. nov.). Pentasacme championii Benth. is considered as a synonym of P. caudatum Wall. ex Wight.