Environmental Effects 



31 



other parts will remain white. The sun-red gene, therefore, reacts 

 to produce a white ear if the environment of the ear is complete 

 darkness but produces a red ear if the ear is developed in the 



Fig. 9. Red and white ears in maize. The left ear is white and the 

 right ear is a red pericarp t3^pe. The two center ears are of the sun-red 

 type and are white where covered and red where exposed to the sun. The 

 red pericarp t3^pe is red whether covered or exposed. The few colored 

 grains in the white part of the sun-red ears are the result of stray pollen. 

 (Photographs by Dr. W. Brooks Hamilton.) 



light. This is a different gene from the normal red pericarp gene, 

 which produces red ears no matter whether the developing ear 

 is kept light or dark. 



The effect of temperature on the gene vg in Drosophila melano- 



