Abstract
Cytological studies have been carried out on ten different species and varieties belonging to two genera of Araliaceae, viz. Aralia and Polyscias. A detailed analysis of karyotypes has been performed in all of them.
Striking uniformity in the chromosome number (2n=24) has been emphasized and the report 2n=36 chromosomes has been made for the first time and the twelve chromosomes appear to constitute the basic set in the family.
Although gross homogeneity in the karyotype among the members of the two genera is noticed, yet a critical analysis shows that each species and variety is characterized by the distinctive karyotype of its own, particularly in the nature of the secondary constrictions.
Taking into account all these facts, it has been considered that structural alterations of chromosomes have been the prime factor in evolution within the family.
The cytological data indicating homogeneity in chromosome number and gross similarity in karyotypes taken in conjunction with the marked similarity in external morphological characters suggest that the different genera of the family are very much interrelated. Nomenclatural changes and the transference of a species from one genus to another as done in the family has been emphasized in this connection.
