Taxonomic Studies of Podostemaceae of Thailand. 2. Subfamily Tristichoideae and Subfamily Podostemoideae with Ribbon-like Roots
This paper revises the taxonomy of the species with ribbon-like roots of subfamily Podostemoideae and all species of sub family Tristichoideae in Thailand. The Tristichoideae comprise Dalzellia with four, all new, species (D. angustissima, D. kailarsenii, D. ranongensis, D. ubonensis); Cussetia (gen. nov.) with C. diversifolia, which is transferred from Dalzellia, together with C. carinata of Cambodia and Laos; and Terniopsis with three new species (T. brevipes, T. ramosa, T. ubonensis) and one new record for Thailand (T. malayana). Malaccotristicha is referable to the emended genus Terniopsis. The subfamily Podostemoideae includes Paracladopus chiangmaiensis (gen. & sp. nov.), Cladopus, with two species, of which C. fallax is a new record, and Polypleurum with nine species, seven of which and one variety are new (P. erectum, P. longicaule, P. longifolium, P. longistylosum, P. phuwuaense, P. rubroradicans, P. wallichii var. parvum, P. wongprasertii). A previous paper reported 13 species assigned to three genera of Podostemoideae with crustaceous roots. In total, nine genera and 34 species of Podostemaceae occur in Thailand, indicating that Thailand, like southern India and Sri Lanka, is a center of distribution for the family in Asia.