Corn Investigations 
51 
means of artificial control in order to avoid contamination. 
This is accomplished by transferring the pollen of one strain to 
the ear of another strain in the same manner as has been de- 
scribed on page 43 for the production of pure lines. When the 
resultant seed is planted, the first generation (F x ) hybrid plants 
Strain No. 
Orig. 8 2 5 1 4 10 12 
Fig. 13. — Typical ear of Hogue’s Yellow Dent corn at left. At right, 
typical ears of seven distinct pure lines of the same variety after 
six years of self-fertilization. The yields for these strains in 1916 are 
given in Table 14, and were respectively: Original, 37.5 bu.; 8, 
10.8 bu.; 2, 8.0 bu.; 5, 3.1 bu.; 1, 14.5 bu.; 4, 2.3 bu.; 10, 15.4 bu.; 
and 12, 14.8 bu. per acre. 
are produced. In figure 14 are shown representative plants of 
each of ten different F 1 hybrid combinations among the ele- 
mental strains shown in figure 12. Many other combinations of 
these seven strains have been grown and all showed increased 
vigor except the cross between strains 8 and 10. These two 
strains, altho originating from entirely different stock, do not 
differ materially in any visible character except in color of the 
midrib of the leaf and leaf sheath. Strain No. 10 has an orange- 
colored midrib, while No. 8 has a green midrib. It is likely that 
they are nearly identical in the Mendelian factors associated 
with vigor of growth. No extensive detailed study has been 
