Cytological Studies in the Cycads: Sex Chromosomes in Cycas

The chromosomes of Cycas pectinata are studied from root tipand pollen mitoses. The male and female plants showed the samenumber of chromosomes (2n = 22) with almost identical chromosomemorphology. The only difference is that in the female planttwo chromosomes of the somatic complement (pair III) bear satellites,while in the male the same pair is heteromorphic with only oneof its members bearing a satellite. This becomes further clearwhen two types of haplid complements are noticed in pollen mitosis,one type possessing a satellited chromosome, and the other showingnone bearing a satellite. The pair of chromosomes which is heteromorphic in the male isassumed to be associated with sex determination in Cycas, themale being the heterogametic sex with XY type of sex chromosomes.