Karyotype Analysis of Bulbous Iris

Karyotype analyses were made of species and garden varieties of bulbous irises, including I. winogradowii (2n = 16), I. histrioides var. Major (2n=16), I. histrioides (2n=17), I. reticulata var. Violet Beauty (2n=18), I. reticulata var. Clarette (2n=20), and I. danfordiae (3n=27). 2. I. winogradowii has 8 pairs of chromosomes, including 2 pairs of metacentrics, of which 1 has a truly median centromere. The remaining chromosomes are acrocentric with subterminal centromeres. 3. I. histrioides var. Major has 8 pairs of chromosomes, of which 3 pairs are metacentric, and 2 of these have median centromeres. Another form of this species has an extra fragment-like chromosome with a subterminal centromere in addition to the regular 8 pairs. 4. I. reticulata var. Violet Beauty has 18 chromosomes, a new number for this species, and the presence of unpaired chromosomes indicates that it is a hybrid involving plants of unlike chromosome morphology. The Clarette variety of this species has 20 chromosomes, mostly unpaired and obviously of hybrid origin. 5. I. danfordiae has 27 chromosomes, including 3 identical sets, apparently of autotriploid origin. 6. The natural affinities of these species of bulbous iris are discussed primarily from the standpoint of similarities and differences in their karyotypes.