Neo-Mendelism 



61 



result that the color character is modified. The mech- 

 anism of this situation will make clearer the behavior 

 of the supplementary factor. If C is the chromogen 

 and R the enzyme, what is P? The suggested answer 

 can be obtained from plant chemistry. It is found 

 that the purple pigment is produced by the same sub- 

 stance as the red, but represents a higher state of oxida- 

 tion. The conclusion is obvious. C is oxidized by R 

 up to a certain point, where red is produced; but if P 



Purple Red White 



FIG. 13^. Diagram illustrating action of supplementary factor 



is also present it represents an additional enzyme, which 

 attacks the red pigment and oxidizes it still further into 

 purple. P is incapable of attacking the original chromo- 

 gen, but when R carries the attack to a certain point, 

 P can function and carry the oxidation further. As 

 a consequence P without R gives white grains, while R 

 gives red grains only in the absence of P. 



4. CUMULATIVE FACTORS. These will be considered 

 under the next heading, " Inheritance of quantitative 

 characters." 



In addition to the four types of factors given, 

 the literature of genetics also contains discussions on 



