390 



far as I know, the flora of the sea has not been examined in 

 this respect, and it is obvious that a comparison would be 

 very misleading if it were based on the quantities of CO^ 

 present in the water and in the air, respectively. If the law 

 holds good for marine Algae the assimilation must be propor- 

 tional to the amount of free carbonic acid — that is to the 

 tension ^) — , and the growth of the plants must not unfrequently 

 be seriously hampered by want of carbonic acid, though the 

 gas may be present in considerable quantities. 



') An experimental investigation of this problem will now Le comparatively 

 easy if my method of tension-determination be adopted. 



