Cytotaxonomy of Ficoideae

Abstract

Cytological investigations on 15 species of Ficoideae of Bentham and Hooker have been worked out with the aid of improved methods. A homogeneity in chromosome number and structure in all the genera has been found. The acceptance of the status of Ficoideae (or Ficoidaceae) embracing all these genera under three tribes as created by Bentham and Hooker has been stressed. The tribe Aizoideae having a basic set of 8 or 9 and with a wide range of habit and habitat is the most primitive among these three tribes. Two separate evolutionary lines emerged from the Sesurium-like ancestral stock, one led to the terrestrial forms of the tribe Mollugineae and the other to pure succulents of the tribe Mesembryeae. Both the above tribes have predominantly a basic set of 9. The genera like Trianthema, Tetragonia with a basic set of 8 chromosomes seem to be derivations adapted to certain conditions of environment.
Lastly, the occurrence of variation in chromosome numbers in two species has been discussed and the need of investigations in this direction concerning the relative importance of sexual and vegetative means of speciation in this family has been stressed.