VI 
PREFACE 
treats such varied subjects as the new discoveries which 
have made for progress by improving human environment ; 
quarantine regulations for the protection of domestic fruits 
from foreign destructive insects; the functions of the United 
States Department of Agriculture; and the principles of 
variation and heredity as they affect both the cultivation 
of the soil and human life. 
May, 1920. 
W. M. S. 
I. L. R. 
G. A. B. 
