CHARACTERISTICS: RELATION TO ENVIRONMENT 245 



the difference in color is inherited; it is due to gene diversi- 

 ties. But a certain variety produces red flowers when grown 

 in a cool place, white flowers when grown in a warm, moist 

 region, as in a greenhouse. The same diversity in color is 

 now due to an environmental difference. 



Complex interrelations of genetic and environmental ac- 

 tion have been described by Emerson with relation to di- 

 verse colors in maize plants.^ In different types, the leaves, 

 the husks, the flowers, and other parts, differ in color. 

 Emerson describes and figures six main types, under each 

 of which are subtypes. These are the following: 



1. Purple, with its subtype weak purple 



2. Sun-red, with a subtype, weak sun-red 



3. Dilute purple 



4. Dilute sun-red 



5. Brown 



6. Green, with a number of subtypes. 



The interrelations of genetic and environmental factors 

 in these colors may be summarized as follows: 



A. Each color and each subtype is constant and heredi- 

 tary, when the different types are bred under like condi- 

 tions. 



B. The colors each depend on many different genes, like 

 the eye color in Drosophila; they may be altered by 

 changes in any of these genes. The different colors result 

 from different combinations of the genes. 



C. When the different types are crossed they give typi- 

 cal Mendelian inheritance: in some cases with simple ra- 

 tios, in others with complex ratios. 



Thus far the conditions are those for typical hereditary 

 characters; the differences are the result of gene differ- 

 ences, and they follow the distribution of the different types 

 of genes in inheritance. 



But also, the colors depend on the conditions to which 

 the plants are subjected while developing. Change of cer- 



