358 TENETICS IN RELATION TO AGRICULTURE 
hill and to state the yield of each of the four plants as a percentage of the mean of 
the hill in which it grew. The percentage standing of each kind in all the hills 
was then averaged to secure the final expression of the relative behavior of the 
four kinds. 
“This method of comparison is similar to the ingenious plan originated by 
C. H. Kyle, for use in ear-to-row breeding. Kyle’s method is to plant each of 
the ears to be tested in a separate row and in each hill to plant one seed of a stand- 
ard, or check, ear with which all ears are compared. Since comparative and not 
absolute yields are desired in the study of hybrids and with only four kinds to 
compare, the introduction of a check in the present experiment would have 
increased the space occupied by the experiment without lessening the experi- 
mental error.” 
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Fic. 149.—Parents and Ff, hybrid between two sub-species of Zea mays: Hall’s Tyler 
dent (left), Brewer’s flint (right) and hybrid (center). The hybrid yielded 9 per cent. 
more shelled corn than the dent and 20 per cent. more than the flint and proved the 
most productive of all varieties and crosses in the 1913 test. (After Hayes, Conn. A. E. 8.) 
Crossing Species, Sub-species, Varieties and Local Strains.—Many 
experiments have been made to test the increase in productivity of Fy 
hybrids between more or less closely related forms of maize. As it is 
impossible to review them all, we give as an illustration Collins’ summary 
of the results of 16 crosses made in 1908 between corns of diverse types 
and from widely separated localities. The classification indicated by 
Collins’ descriptions ave as follows: Zea mays indentata (starchy or dent 
varieties)—Maryland, Kansas dent, Brownsville, Chihuahua, Mexican 
dent, Xupha (semi-starch); Zea mays amylacea (floury variety)— 
Tuscarora; Zea mays everta (pop)—Cinquantino, Algerian, Tom Thumb; 
Zea mays indurata (flint)—Guatemala red, Salvador Black; Zea hirta 
Bonafous—Hairy Mexican, Huamamantla, Arribenio; Uncelassified— 
Hopi, Chinese (waxy endosperm), Quezaltenango Black, Quarentano. 
The yields of the 16 crosses and of their parents are given in Table 
LI. 
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