26 Bulletin 392 



Magenta crossed with dark purple. — Four crosses are recorded in this 

 class. They gave all dark purple Fi plants, with the exception of cross 174, 

 which gave 4 dark purples and i light purple. In this case either of the 

 parents might be supposed to have been simplex for I, thus allowing the 

 light purple to appear in Fi. The others need no further explanation 

 than to point out that such a cross could result in only purples, due to 

 the dominance of the blue over the red. 



Type 6 Light blue (Plate I) 



Light blue crossed with light blue. — In cross 140 the single Fi plant 

 was dark blue. This can be understood if one or both of the light blue 

 parents bore' X in simplex condition. In recombination there might 

 result a duplex condition of the gene that would cause the dark blue type. 

 No other cross is recorded in this class. 



Light blue crossed with mauve. — In cross 106 the Fi plants were all dark 

 blues, and these split in Fo into dark blues, mauves, and pinks. In this 

 case the mauve parent probably brought in the intensifying gene X, 

 which reacted with the gene B from the light blue parent and gave dark 

 blue in the hybrids. If both X and B were simplex in these Fi hybrids, 

 the recombinations in F2 would cause dark blues, light blues, mauves, 

 and pinks. 



Light blue crossed with dark blue.— Cross 216 gave i dark blue and 2 light 

 blues in Fi. This is to be expected on the hypothesis that the light blue 

 parent is simplex for R. A hybrid, then, having both R and X simplex 

 would not be a dark blue but a light blue, as shown in the following schema: 



Fi 

 CCRrBBxx light blue f RRBBXx dark blue 



X CC< 



CCRRBBXX dark blue [ RrBBXx light blue 



In cross 115 the Fi consisted of 4 purples, showing the light blue parent 

 to have been duplex for R. 



Light blue crossed with dark purple. — The two crosses in this class 

 gave dark purples and light purples in Fi, which split into light purples, 

 dark blues, and i white in F2. In such crosses the intensifying factors 

 X and I would be expected to be simplex in the Fi plants, resulting in 

 purple, but not of the deep, intense hue of the darker type. 



Type 7 Dark blue (Plate I) 



Dark blue crossed with dark purple. — Six crosses give data for this class. 

 In Fi there were 12 dark purples and 4 light purples; in Fa there were 



142 



