A NEW LINE OF CHROMOSOMAL EVOLUTION IN ISOETES

Based on plants which exhibit a series of multiples of n = 12 chromosomes, a new line of chromosomal evolution has been suggested. The possible origin of this series of 12, besides of n = 10 and n = 11 has been suggested due to the instance of chromosomal fission at an early phase of evolution. Role of chromosomes with enough heterochromatin is understood to play a key role in this mechanism.

I. muricata is reported from Bhopal, India, inhabiting similar moist grassy rocks as reported from Australia. Root tip mitosis has shown 2n = 60 chromosomes which is a new count for this species. I. pantii has shown three cytotypes with 2n=24 (15)% ,2n = 36 (60% plants) and 2n = 48 (25% plants) chromosomes. Another species partly resembling I. pantii possesses 2n = 72 chromosomes.