Abstract
Chromosome numbers are reported for 15 species of Dioscorea and Rajania. All are multiples of the base number, 9. Three new cases are reported of both 36 and 54 chromosome plants in a single species. The possible modes of origin of hexaploids are discussed. Colchicine induced octoploids were used to synthesize 54 chromosome plants of D. floribunda. All such hexaploids were highly infertile. Guard cell lengths were correlated with level of ploidy and provided a rapid screening technique for finding higher polyploids.
