1922] Setchell-Goodspeed-Clauseu: Nicotiana Tahacum 499 



In the segregation the same grading as before of the pinks into 

 two intergrading classes in the proportion of approximately 2 inter- 

 mediate pink : 1 light pink was observed, but it was even more difficult 

 to draw a line between light pink and intermediate pink because of 

 the effect of the hose-in-hose conditon on flower color expression in 

 those plants which bore teratological flowers. In the matter of segre- 

 gation into normal and hose-in-hose flowers, some difficulty was ex- 

 perienced because some otherwise normal flowering plants bore some 

 flowers which showed a tendency for the calyx to become petaloid, 

 and others bore flowers which showed a very slight hose-in-hose ten- 

 dency. A correspondingly slight hose-in-hose tendency is also present 

 in Fj plants. These plants were classified as normal. Here again it 

 can be seen that the segregation ratios of 144 pink : 54 red and 151 

 normal : 47 hose-in-hose are in substantial agreement with Mendelian 

 expectation for contrasts in a single pair of allelomorphs in each case. 

 Moreover, the dihybrid ratio is substantially in agreement with that 

 expected for independent segregation of the members of these two pairs 

 of allelomorphs. 



4. F3 AND SUBSEQUENT GENEEATIONS OF THE CALYCINA-VIRGINICA 



SERIES 



In 1912 twelve F3 families of Hjg and five of Ho,, were grown. They 

 will be grouped for consideration according to the characters which 



TABLE 10 



Fa BEHAVIOR OF RED SEGREGANTS. » 



the F, parent exhibited. In table 10 the data with respect to the be- 

 havior of F3 populations from red flowering F2 plants are collected. 

 Five such populations gave nothing but red flowering plants, indicating 

 clearly that red segregants breed true. In table 11 the data from pink 

 flowering plants are similarly collected. The reader will not fail to 

 notice that some pink flowering selections were not heterozygous for 



