180 



HANS RASMUSON 



of the white-flowered F^-plants showed a small lamount of red pigment 

 in the stem. Then the theoretical ratio as to the stem colour would 

 be 9 true red : 3 slightly tinged with red : 4 green, as the plants with 

 only B or without A and B are green. The numbers found in the 

 hybridisation II were 16 red, 9 tinged with red and 10 green. As the 

 calculated numbers are 19,6875 + 2,935, 6,5625 + 2,309 and 8,75 ± 2,562 the 

 facts agree very well with the theoretical values. 



On this hypothesis the Fn-generations of the Fi-plants AaBb 

 would consist of the following types. 



/9 



1 AABB lilac flowers, red stem 



2 AABb » » 

 2 AaBB » » » » 

 4 AaBb » » » » 



1 A Abb white » tinged » 1 



2 Aabb » ' » » » J 



1 aciBB » » green » | 



2 ctaBb » » » » > 4 

 1 aabb » » » » ] 



If the genotypes A Abb, Aabb, aaBB and aaBb have white flowers 

 and the genotype AaBb has lilac flowers it must be possible to obtain 

 lilac-flowered plants by crossing two white-flowered individuals. If 

 one of these is AAbb or Aabb and the other aaBB or aaBb some of 

 Ihe Fi-plants become AaBb. The difficulty consists in selecting 

 the two plants to be crossed. The plants with only A can be 

 recognized on the red-tinged stem but the plants with only B can 

 not be distinguished from those of the constitution aabb. If, however, 

 one Fo-plant with red-tinged stem is crossed with several Fa-plants 

 with green stems some of these must contain B. This must 

 be the case, theoretically, with three out of four green-stemmed Fa- 

 plants. In some crosses plants with both A and B must be present 

 and consequently lilac-flowered individuals be obtained. Of such 

 crosses I have made the following ones. 



II— 9— 2 white flowers, stem green X H— 9—1 white flowers, stem tinged with red. 

 II— 9— 4 » » » » XII— 9— 3 » » » > » » 



11—9—5 » » » » XII— 9— 3 » » , , » » 



II_9_6 » » » * xn-9— 3 » ^ » ». » 



II— 9— 7 » » » » XII— 9-3 » . » . ^ » » 



In the first cross only one plant was obtained which had white 

 flowers and green stem. In all the other crosses the same plant with 



