THE EXPERIMENTAL STUDY OF GENETIC RELATIONSHIPS 1 55 
There should be some discrimination between true synonyms, which 
are names appHcable to the same identical organism, and the names of 
distinct units which it may not seem desirable to differentiate in a 
popular manual. 
The problem of genetic relationships is the greatest problem of 
biology. Only repeated attacks, from every side, will solve it. It is 
no reason for pessimism that results come slowly. Centuries may 
pass before the greater trends of evolution will be understood. In 
the meantime we must not scorn our advances, even though they seem 
slight. 
Bureau of Plant Industry, 
Washington, D. C. 
