PLATE III 
Tue Errect or Soil Depth upon Earty DEVELOPMENT 
Fic. 1. The effect of soil depth upon the development of Pinus pon- 
derosa (S. D.). Ten plants grown (1) in deep, (2) in medium, and (3) 
in shallow soil. ™% natural size. 
Fic. 2. The effect of soil depth upon the development of Robinia pseu- 
dacacia. Three plants each (1) grown in shallow, (2) in medium, (3) in 
y 
deep soil. 1% natural size. 
