Abstract
Seven taxa belonging to two species of Iberis have been dealt with in the present scheme of work. Members of I. amara reveal uniformly 14 chromosomes, while all the four varieties of I. umbellata have 18 chromosomes in their somatic complements indicating the existence of basic complements with 7 and 9 chromosomes. Results show close relationships between the basic sets and suggest as well the probable derivation of 9 from 7. The complement of 7 chromosomes may be regarded as primarily basic to the genus Iberis.
In spite of the remarkable constancy of chromosome number in the varieties of a species, they, however, differ in the details of chromosome morphology suggesting that structural alteration of chromosomes has also been an important factor in diversification of the genus. Most primitive karyotype is represented in I. amara from which other species and varieties might have evolved through aneuploidy and structural changes of chromosomes.
