PHYSIOLOGY 



293 



The light relations in the photosynthetic mechanism of the 

 algae can be divided into two components : 



(a) Physical component, which is the amount of light energy 

 absorbed by the thallus. 



(b) Physiological component, which is the amount of absorbed 

 light energy that is actually employed in carbon assimilation. 



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Weight 

 Fig. 187. Chlorophyll content of the same number of red, green and brown algae 

 expressed in different terms. (After Seybold and Egle.) 



The light energy relations of selected members in the Chloro- 

 phyceae, Phaeophyceae and Rhodophyceae are illustrated in Table 

 XI from Seybold (1934) and also in fig. 188. 



It is at once obvious that at depths below i m. the Rhodophyceae 

 and Phaeophyceae are much more efficient as metabolic machines 

 than the Chlorophyceae, and several species are even more efficient 

 at the surface. As a resuh of his studies Seybold (1934) concluded 

 tliat Englemann's theory of complementary colours is only valid 

 for the physical component of the light relationship, that is, the 



