58 



HEREDITY AND ENVIRONMENT 



K 



Fig. 18. Phototropism of Seedling of White Mustard sup- 

 ported by a sheet of cork (K, K) floating on water. The di- 

 rection from which light comes is shown by arrows; the stem 

 and leaves are turned toward the light (positive phototrop- 

 ism), the root away from the light (negative phototropism). 

 (After Strasburger.) 



