CHAPTER II. SPECIAL PHYSIOLOGY OF THE NUTRITIVE FUNCTIONS. 715 



4 3125 



FIG. 471. Water-cultures of Buckwheat (after Nobbe). 

 No.l. Plant grown in normal solution. 



3. 

 4. 

 .. 6. 



without potassium. 



with sodium-salts instead of potassium. 



without calcium. 



without nitrates or salts of ammonia. 



This method of experimental culture, which is known as water- 

 culture, has been of the greatest service in determining which are 



