Abstract
At interphase nuclei of Rumex acetosa, two Y-chromosomes and H-segments of certain autosomes usually reveal themselves as chromocenters. In each sex of the species, two different clones, one bear H-segment and the other no such segment, were studied for counting the chromocenters in relation to H-segment-bearing autosomes, to the Y-chromosomes and to both the autosomes and Y's.
In female, the number of chromocenter corresponds to that of H-segment-bearing autosomes. In male, the chromocenters are more in number than the Y-chromosomes in one clone and also more than the Y's plus the H-segment-bearing autosomes in the other clone. Supporting our earlier study, the above facts seem to show that the heterochromatin of Y-chromosomes has a tendency to gather euchromatin granules into a mass which must be treated as a chromocenter, and that the heterochromatin of autosomes has no such a tendency.
