Smithsonian Report, 1938. — Hoagland and Arnon 



Plate 2 



1. Effect of forced aeration on asparagus plants grown in culture solutions. Right: plants without forced 

 aeration. Left: plants grown in solution through which air was bubbled continuously. 



2. The asparagus plant on the left grew in a nutrient solution in which boron, manganese, zinc, and copper 

 were present in such small amounts as one part in several million parts of solution; those on the right grew 

 in solutions to which these elements were not added. 



