1. Six chromosomal formulas of the intersexual plants of Rumexacetosa L. were determined as follows, Chromosome-number Chromosomal formula 15 13a+X+Y 15 11a+X+2Y+y 15 12a+X+Y+y 15+1f 12a+X+2Y+1f 15+4f 12a+X+2Y+4f 22 18a+2X+2Y (f=fragment) 2. The y-chromosome which is sometimes discovered in the intersexual plants seems to be the chromosome formed as the result of fusion of the two bifurcate unequal arms of the Y-chromosome. This conclusion was drawn from various reasons, especially from the result of quantitative considerations. 3. The y-chromosome and the chromosome-fragments are considered to have a relation to or an influence on the expression of the sexual characters.