SOLUTION AND SAND CULTURES 



433 



sand culture method has been used. Aluch valuable information regarding 

 the specific sj-mptoms of the deficiency of the essential elements in many 

 species of plants has been obtained by this method. By comparing the develop- 

 ment of individual plants of a species rooted in a "complete" solution with 



Fig. 97. A "drip culture." Redrawn from Shive and Robbins (1938). 



the development of other plants of the same species rooted in a solution lack- 

 ing in one of the necessary elements, it is possible to determine the distinctive 

 symptoms of a deficiency of that element in plants of that species. Sand and 

 culture solutions are also used in studies of the mechanism of the absorption 

 of ions, and the toxic effects of various ions on plants. 



The fact that it has been found possible to grow many species of plants 



