A contribution to the cyto-taxonomy of Brassica (Cruciferae) and its allies

Material of 85 species of Brassica and genera closely related to it was examined cytologically, and the chroiftosome counts are reported. These confirm records published by other workers for 42 species, two contradict earlier records, and 41 counts are believed to be new. Different species with the same chromosome number have been cross-pollinated, and those found to be interfertile have been grouped into cytodemes. For the most part species found to be interfertile have long been regarded as closely akin, but three cases of interfertile intergeneric hybrids are reported. Altogether the material has been classified into 45 cytodemes: 35 diploids with chromosome numbers ranging from n= 7 to n= 13, and 10 derived tetraploids. This enumeration is possibly not exhaustive of the world's genomes closely related to the crop Brassicas and a list is appended of the wild species which need examination before the enumeration might be considered to be complete.