COLLATERAL READING 



317 



the chlorophylls are heavier than those of the carotinoids, the relative number 

 of molecules of each of these pigments present is not indicated by the data 

 in Table 28. Certain data illustrating this point are presented in Table 29. 



TABLE 2Q MOLECULAR PROPORTIONS OF THE CHLOROPLAST PIGMENTS PRESENT IN LEAVES 



AT DIFFERENT SEASONS (dATA OF WILLSTATTER AND STOLL, I918). 



As shown in Table 29 green leaves usually contain about three molecules 

 of the chlorophylls to every one molecule of the carotenoids, about three mole- 

 cules of chlorophyll a for every molecule of chlorophyll h, and about two 

 molecules of xanthophylls for every molecule of carotene. In autumn the 

 carotinoid pigments become relatively more abundant due to the gradual dis- 

 appearance of the chlorophylls and the proportion of xanthophylls to carotene 

 in the leaves also increases. 



Suggested for Collateral Reading 



Duggar, B. M., Editor. Biological effects of radiatioti. McGraw-Hill Book 



Co. New York. 1936. 

 Palmer, L. S. Carotinoids and related pigments. Chemical Catalog Co. 



New York. 1922. 

 Spoehr, H. A. Photosynthesis. Chemical Catalog Co. New York. 1926. 

 Stiles, W. Photosynthesis. Longmans, Green and Co. London. 1925. 

 Willstiitter, R., and A. Stoll. IJnterstichiingen ilber die Assimilation der 



Kohlensdure. Julius Springer. Berlin. 191 8. 

 Willstatter, R., and A. Stoll. Investigations on chlorophyll. Translated by 



F. M. Schertz and A. R. Merz. Science Press. Lancaster, Pa. 1928. 



