Sex-limited inheritance in Lychnis dioica L. 



277 



In this table again is seen the nearly total absence of females, 

 there being only 12 to offset 1644 males, and of these few females, 

 8 occurred in a single rather small family, leaving to the remaining 

 21 families only 4 females among 1590 individuals. We might almost 

 conclude that the narrow-leafed Fs males were negative homozygotes 

 with respect to the sex-gene F as well as its usual companion, the 

 broad-leaf-gene, B. That narrow-leafed males need not be so constituted 

 as to produce only male offspring, however, we have already seen, for 

 the original narrow-leafed mutant gave 10 per cent females in my cultures 

 and 42 per cent females in those of Dr. Baur. 



Lea\ing aside this peculiar absence of females, we are now pre- 

 pared to show from Tables I and II that the first deduction from the 

 formulation proposed for the genotypic constitution of the broad-leafed 

 and narrow-leafed types, has been realized; namely, it has been shown 

 that the 32 broad-leafed females in the F2 famüy (No. 11335) were 

 genotypically of two kinds, though phenotypically all were alike. Table I 

 shows that 15 were heteroz\'gous. Table II that 17 were homozygous, almost 

 exactly the equal numbers of these two types, which were to be expected. 



(c) Crosses betireen the broad-leafed F-^ males and their heterozygous 

 female sibs. 

 According to our hypothesis, all of the broad-leafed males in the 

 Fa family should have been heterozygous for the gene B, and therefore 

 of the same genotype as the Fi males. When crossed with their hetero- 

 zygous sibs, if this h^ijothesis holds, they should give in the Fs a 

 repetition of the phenomena seen in ¥«; i.e., there should appear again 

 the three phenotypes, broad -leafed females, broad -leafed males and 

 narrow-leafed males, in approximately the series 2:1:1. The essential 

 attainment of this expected result is shown in Table III. 



