3. Thismia Griffith, Proc. Linn. Soc. London. 1: 221. 1845.
水玉杯属 shui yu bei shu
Plants annual, without chlorophyll, mycotrophic; tuberous. Stems simple or branched. Leaves cauline, bractlike, small. Flowers 1-4, terminal. Perianth tube actinomorphic to zygomorphic, cylindric, urceolate, or sometimes campanulate, with prominent annulus at mouth, lateral wings absent; tepals 6, apically distinct; outer tepals as long as or shorter than inner tepals; inner tepals sometimes apically connivent or connate into an erect mitre. Stamens 6, generally laterally connate, pendent from annulus, occasionally distinct; connectives with 0-2 apical and 0-2 basal appendages. Ovary obconic or obovoid, 1-loculed, with 3 parietal placentae; stigmas 3, simple or bilabiate. Fruit fleshy with persistent perianth base; dehiscence by abscission of apex.
About 43 species: pantropical; two species (one endemic) in China.
Phylogenetic relationships within the Dioscoreales remain uncertain: Thismia may be sister to Tacca J. R. Forster & G. Forster (hence warranting recognition as a distinct family, Thismiaceae), although the Thismiaceae may be paraphyletic (V. Merckx et al., Amer. J. Bot. 93: 1684-1698. 2006; V. Merckx & M. I. Bidartondo, Proc. Roy. Soc., B, 275: 1029-1035. 2008; V. Merckx et al., Cladistics 25: 64-77. 2009).
