Plate 20. — Growth of tomato plants in three 

 types of culture; soil, sand, and solution. All cul- 

 tures yielded at the same order of magnitude, 

 when grown side by side in the greenhouse. All 

 yields of fruit were very large. (From Arnon and 

 HOAGLAND, 1940). The solution culture technique 

 was that devised by W. F. Gericke. 



