Taxonomic Studies of Podostemaceae of Thailand. 1. Hydrobryum and Related Genera with Crustaceous Roots (Subfamily Podostemoideae)

Abstract

Recent field work and collections, along with herbarium work, have discovered that three crustaceous-rooted genera with 13 species of subfamily Podostemoideae occur in Thailand. They are two species of Hanseniella, one of which (Ha. smitinandii) is new, the recently described genus and species, Thawatchaia trilobata, and 10 species of Hydrobryum, including six new species and one new variety: Hy. chiangmaiense, Hy. kaengsophense, Hy. khaoyaiense, Hy, loeicum, Hy. somranii, Hy. tardhuangense, and Hy. micrantherum var. crassum. Thailand is a center of distribution for the monophyletic group of Hydrobryum, Hanseniella and Thawatchaia, which are distributed throughout Thailand except in the peninsular. All the species and varieties are described. A key to the species, a table of diagnostic reproductive characters, lists of synonyms and illustrations are provided.