1.- Chromosome numbers in the genusBothriochloarange from 2n= 40 to 2n= 180 in multiples of 10.2.- Meiotic behavior varies from very regular in the New World species to very irregular in some of the Old World species.3.- Occurrence of aneuploidy is very rare in natural species ofBothriochloa.4.- Intergeneric and interspecific hybrids involving parents at different ploidy levels, can be obtained in the Bothriochloininae.5.- Occurrence of aneuploidy is common in some hybrids.6.- The extra chromosomes in the aneuploid plants do not differ in size or morphology from the normal chromosomes in the basic complement.7.- In the New World species ofBothriochloa, absence of aneuploidy seems to be correlated with cleistogamy and regular meiosis.8.- In the Old World species ofBothriochloa, a high degree of apomixis and some form of natural selection for complete genomes seem to be the reasons for extremely rare occurrence of aneuploid plants in nature.9.- In areas where forms ofBothriochloawith a high degree of sexuality are found natural aneuploids may be present.