Abstract
The new genus Allophylastrum (Sapindaceae) is described from Roraima, Brazil and Guyana. Allophylastrum resembles the genus Allophylus in its vegetative morphology but differs by its apetalous flowers with a cupular nectary disc, 5-6 unequal stamens, and 4- to 5- porate pollen grains. A key is provided to differentiate Allophylastrum from Allophylus. The new species Allophylastrum frutescens is described and illustrated.