58 BULLETIN 1489, U. S. DEPARTMENT OF AGRICULTURE 
for the specialized plant breeder in so far as isolating lines that 
produce the high-yielding crosses is concerned. The function of the 
farmer will be in producing seed for commercial planting of those 
combinations that have been proved to be high yielding. Selection 
within selfed lines still is in an experimental stage and its benefits 
will not be available generally for some years. In the meantime 
advantage should be taken of whatever crosses may be proved to be 
more productive in the different sections. By mass selection the 
yields of the better existing varieties may be maintained and possibly 
increased. Mass selection primarily is the method for the farmer to 
use in producing either his own seed com or seed corn for sale. 
Moreover, it is the only method that can be recommended for the 
use of the farmer at the present time. Between careful mass selec- 
tion on the one hand and selection within selfed lines on the other, 
no method of corn breeding that has been tried has offered enough 
advantage to warrant its recommendation. 
