| Abstract: | Two new genera are described while a systematic study on the genus Siraitia (s. l. ) is made. Siraitia Merr. (s. 1. )contains seven or eight species, some of which were placed in the genus Thladiantha Bunge(Cogniaux 1881, 1916, Jeffrey 1962)until 1981 (Lu & Zhang 1981 ). Though Siraitia as a genus was des cribed in 1934, it has not been properly circumscribed up to now. Siraitia (Jeffrey 1980)was divided into three subgenera (Zhang & Lu 1989)which in this study are raised to three genera: namely Baijiania1） A. M. Lu et J. Q. Li, gen. nov., Microlagenaria (C. Jeffrey) A. M. Lu et J. Q. Li, gen. nov. and Siraitia Merr. Baijiania is clearly discriminated from Siraitia by non-glandular scales, entireleaf-blades racemose, 5—8-flowered male inflorescences, large, heterogeneous, glabrescent or sparsely hairy sepals, reniform anthers , wingless seeds thick extine and chromosome number 2n = 32. The genus Microlagenaria, which is only distrib uted in Africa is situated between Baijiania and Siraitia in phylogeny, but more closely related to the latter (Plants with glandular scales; leaf-blades 3-5-obed; male inflorescences racemose, many-flowered; sepals small, triangular; anthers reniform, curved; female flowers solitary or 8-13-flowered, clustered on a short (2cm) peduncle). A key to the genera is as follows:1. Plants without glandular scales 2. Tendrils coiling above the forking point, anthers erect, 2n= 18 ........................................................ 1. Thladiantha 2. Tendrils coiling both above and below the forking point; anthers curved, 2n= 32 .................................................. 2. Baijiania1. Plants with glandular scales 3. Leaves 3--5-lobed, anthers curved, seeds wingless ........................... ....................................................... 3. Microlagenaria 3. Leaves entire, anthers S-shaped, folded, seeds winged 2n= 38... 4. Siraitia |
