Comparison of Chromosome Types in Disporum

Abstract

1. The number, size and shape of somatic chromosomes in three Disporum species and a variety of one of them were studied, and the comparison of chromosome types was made among them. 2. D. pullum, D. smilacinum, D. smilacinum var. ramosum and a form of D. sessile were determined to have 8 chromosomes in haploid or 16 in diploid. One other form of D. sessile showed 24 chromosomes in diploid. 3. The chromosomes were classified according to the length, relative position of constrictions in them and the presence or absence of satellites. 4. The determination of the length of chromosomes and the relative position of constrictions was made by a special method devised for measuring the true length of chromosomes with foreshortening. 5. On these bases 16 somatic chromosomes in each set of 3 species and a variety were classified into 8 types. 6. In order to compare the chromosome types among different species and variety, the percentage ratio of the whole length and that of the arms formed by the constrictions of each chromosome type were calculated to the sum of the whole length of all chromosomes in a set. 7. Between D. smilacinum and its variety ramosum, all chromosome types are much similar from the standpoint of their relative length and shape. 8. D. pullum, D. sessile and D. smilacinum and its variety ramosum show 5 types of chromosomes which are always similar in their relative length and shape, but if the comparisons are made between two different species of three, 2-3 types are more or less different. 9. The changes in the size and shape of chromosomes may have occurred during the phylogenetic courses of the species. This investigation was carried out in the Botanical Laboratory of the Utsunomiya Agricultural College, Utsunomiya, Japan. I wish to express my sincere thanks to Prof. F. Kagawa for his helpful suggestion and guidance. © 1932, Japan Mendel Society, International Society of Cytology. All rights reserved.