Dioscorea orbiculata Hook. f. and D. tenuifolia Ridl. in Peninsular Thailand and stellate hairs in D. sect. Enantiophyllum Uline

Abstract

Dioscorea sect. Enantiophyllum Uline is characterised by possession of right-twining stems. Most species have opposite leaves and are (sub)glabrous. Only one Asian species, D. orbiculata Hook. f., has stellate or dendroid pubescence. Five African species with the same combination of characters have been classified as a separate section, D. sect. Asterotricha Uline. A comparative morphological study has led to the reduction of the subglabrous D. tenuifolia Ridl. to varietal status within D. orbiculata. This new concept of D. orbiculata possesses a range in indumentum from a few unbranched hairs on young buds to dense stellate or dendroid hairs. It supports the hypothesis that all species of Dioscorea in the Old World which twine to the right should placed in D. sect. Enantiophyllum, rather than infrageneric taxa being separated based on possession of stellate pubescence.