1974 年 39 巻 1 号 p. 17-26
Meiosis was regular in two chromosomal races of Iseilema laxum Hack. with n=14 and n=15 chromosomes. Pachytene chromosomes have similar morphology in the two races. They could be identified from their differential staining reaction, position of centromere, absolute length, presence or absence of prominent chromomeres and nucleolus attachment. The first 14 chromosomes in race 1 were similar to those of race 2. The F1 of the two races has 14 II and 1 I and meiosis was regular except for the univalent. The genomes of the two races are homologous except for the presence of an excess pair of chromosomes in race 1. The extra chromosome is not a B-chromosome as was evident from its morphology and cytological behaviour. It was concluded that chromosome 15 of race 1 does not carry any vital genes or alternatively, the two races may be allopolyploids or secondary polyploids derived from closely related species in which loss of a single chromosome pair may not have serious affect.