| Abstract: | Fifty two taxa have been studied, out of which forty five, including the species; H. citrina, H. dumortierii, H. multiflora, H. forrestii and H. thunbergil are diploid with 22 chromosomes in the somatic complement. H. fulva var. Europa, H. fulva var. cypriana, H. kwanso "Flore Pleno" and H. disticha "Flore Pleno" are triploid with thirty three chromosomes in the somatic complement. One cultivar "Mrs. David Hall" is tetraploid with forty four chromosomes. Besides this two aneuploid clones "Garden Lady" and cv. "29" with 2n=23 and 2n=29 chromosomes respectively were also encountered. Essentially four basic karyotypes are recognizable; A(IV + 8L + 1J + 1I), B(IV + 7L + 2J + 1I), C(9L+ 1J + 1I) and d(8L + 2J + 1I), where V stands for median, L for submedian, J for subterminal and I for terminal centromere. Thirty two taxa could be relegated to these four types and 17 can be resolved as combinations of these four types. These fall under AB, AC, AD or BC, BD and CD classes. The number of nucleolar chromosomes does not show any correlation with the grade of ploidy, whereas 2, 3 or telocentric chromosomes were consistantly found in diploid, triploid and tetraploid taxa respectively. The possible origin of telocentric chromosomes and aneuploid taxa has been discussed. |
