Abstract
In both the female and male plants of Cycas revoluta, somatic chromosome was 2n=22, that is from 1st to 11th pair. The pairs from 1st to 10th were indistinguishable between the two sexes. In the female plant the chromosomes of the 11th pair were homomorphic, both being long and J-shaped. However, in the male plant the chromosomes of the 11th pair were heteromorphic; one is long and J-shaped, the other short and V-shaped. And this J-shaped one was indistinguishable from J-shaped ones of the 11th pair of the female plant. Therefore, the chromosomes of the 11th pair of both sexes are assumed to be the sex chromosomes; _??_ 2n=20+XX and _??_ 2n=20+XY.
