After colchicine treatment of true breeding sorghum varieties, variants without change in chromosome number arose which immediately bred true. It had previously been proposed that colchicine treatment caused the formation,by reductional grouping of the somatic chromosomes, of a cell with a different genotype which, because of its genotypical or positional advantage, took over the growing point to form a homozygous shoot. To determine if chromatin rearrangement had been responsible for the variant plant type, examinations of meiosis in the original material, in the variants and in the F1 hybrids between these were made. Analysis of pairing relationships at pachytene in each of these showed that no detectable irregularity or rearrangement of chromatin occurred. The appearance of new phenotypes, and the apparent recessive inheritance of the green coleoptile characteristic lead to the proposal that the colchicine-induced variants have resulted from gene mutation orcryptic structural changes in thechromatin.