[Chap. XX BIOLOGICAL RELATIONS OF GREEN PLANTS 187 



country in which ignorant, indifferent, uninformed, and ruthless exploi- 

 tation of plants and plant environments should speedily be replaced by 

 intelligent efforts at conservation based upon a knowledge of plants and 

 of their biological relations. 



REFERENCES 



Heinicke, A. J., and N. F. Childers. The daily rate of photosynthesis of a young 

 apple tree of bearing age. Cornell Univ. Agr. Exp. Sta. Memoir 201. 1937. 



Schroeder, H. Die Naturwissenschaften. 70:8-12, 23-29. 1919. 



Transeau, E. N. The accumulation of energy by plants. Ohio Jour. Sci. 26:1-10. 

 1926. 



U. S. D. A., Various Yearbooks contain data on crop yields, animal popula- 

 tions, and industry. Since 1935 these data have been published annually in 

 a volume entitled Agricultural Statistics. 



