2 BULLETIN 1396, U. S. DEPARTMENT OF AGRICULTUR 
simple Mendelian recessives, and the most expeditious and certain | 
way of eliminating these undesirable types was to bring them 
into expression by selfing and reject all lines showing undesirable | 
characters. | 
The early advocates of the isolation of pure lines by intensive 
inbreeding planned to utilize this method as a means of discovering 
the best strains. Vigor was to be restored by crossing two of the 
selected strains or at most by combining two F, hybrids. To con- 
fine the reconstructed variety to such narrow limits seemed a seri- 
ous defect, precluding the realization of maximum adaptability, 
which could be obtained only by maintaining a greater diversity of 
ancestral lines. In this experiment, therefore, an attempt was made 
to resolve a variety of maize into a number of selfed lines and elim- | 
inate the least desirable. The original variety was to be reconsti- | 
tuted by allowing the remaining lines to interbreed. The plan was | 
to reject the poorest rather than to select the best. The results of | 
this method were to be compared with those of ear-to-row crossbreed- | 
ing based on the same foundation stock. | 
An early objection to selfing as a preliminary to selection was that } 
the reduced vigor of selfed strains is an abnormal condition, and 
oe the results might be inapplicable to vigorous crossbred | 
stocks. 
Much progress has been made toward an understanding of the 
nature of the reduction of vigor that follows selfing; but recent exper- 
iments, including those here reported, show that the original objec- 
tion isnot without foundation. It has been demonstrated that high 
performance in a selfed strain is no assurance that superior progenies 
will result when normal vigor is restored by crossing. Notwithstand- 
ing this fact, the idea still persists that homozygous strains represent 
the orginal building materials of which normal varieties are composed 
rather than the mistakes which nature has made. 
DESCRIPTION OF THE EXPERIMENTS 
The experiments were conducted at Sacaton, Ariz., and Sacaton 
June corn was chosen as the variety. This variety was derived from 
“Taguna,’’ a strain of Mexican June corn. The variety had been 
subjected to careful plant and ear selection for a number of years, 
first by E. W. Hudson and later by S. H. Hastings. Thesame method 
of ear selection has been continued to the present time, thus provid- 
ing a base from which to measure progress. 
The variety has proved to be well adapted to Arizona conditions 
and is as uniform and free from abnormalities as most well-bred 
varieties. 
Since 1920 the planting, harvesting, and note taking have been 
under the direction of C. J. King, superintendent of the United States 
Field Station at Sacaton. 
The procedure may be described best by transcribing the original 
directions. 
Foundation stock—Select 20 of the best ears available, shell each separately, 
and divide the seed from each ear into two equal parts. 
Plant two identical blocks, an ear to the row, rows of 50 plants each. One 
block is to form the foundation of the “‘crossed experiment,” the other to form 
the foundation of the ‘‘selfed experiment.”’ 
