UTILIZATION OF HYBRIDS IN PLANT BREEDING 359 
Taste LII.—Yrieups or 16 Maize Crosses COMPARED WITH 
ParentTaL YIELDS. (After Collins.) 
Percentage of 
Yield | Yield | Average | Yield increase of 
of of male} yield of oO hybrid over 
Name of hybrid female | parent,| parents, |hybrid,}| average of 
parent,| pound | pound | pounds parents, 
pounds per cent. 
Ah3, Maryland dent by Hopi............ 1.19 | 0.74 | 0.965 | 1.25 29 
Ahs, Tuscarora by Cinquantino.......... 0.53 | 0.24 | 0.385 | 0.75 95 
Dh, Kansas dent by Chinese............| 0.99 | 0.39 | 0.690 | 1.09 58 
Dhz, Chinese by Chihuahua...........:..) 0.39 | 0.69 | 0.540 | 0.95 76 
Dh3, Hopi by Chine ce eee re lore 0.39 | 0.565 | 1.28 126 
Dhs, Chinese by Xupha................./ 0.39 | 0.63 | 0.510 | 0.54 6 
Dhs, Brownsville by Chinese............ 10.77 | 0.39 | 0.580 | 1.16 100 
Eh, Hopi by Algerian pop.............. | 0.74 | 0.34 | 0.540 | 0.91 69 
Ghz, Tom Thumb by Quezaltenango black.| 0.10 | 0.10 | 0.100 | 0.42 (a) 
Khsi, Brownsville by Guatemala red..... |0.77 | 0.31 | 0.540 | 0.49 -9 
Khez, Guatemala red by Salvador black. .| 0.31 | 0.27 | 0.290 | 0.33 14 
Mhz, Quarentano by Brownsville....... | 0.27 | 0.77 | 0.520 | 0.48 —8 
Mhis, Huamamantla by Hairy Mexican... 0.40 | 0.18 | 0.290 | 0.31 i 
Mhys, Arribefio by Hairy Mexican........| 0.39 | 0.18 | 0.285 | 0.47 65 
Mhi;, Hairy Mexican by Chinese........ /0.18 | 0.39 | 0.285 | 0.61 114 
Mhzs, Mexican dent by Tom Thumb.... | 0.52 | 0.10 | 0.310 | 0.54 (a) 
Average percentage of increase of hy- | 
brids over average parents......... al oe | Foie | aescoereaee eee 53 
(a) Where the yield of either parent fell as low as 0.10 pound per plant the percent- 
age of increase of the hybrid is omitted. In dealing with these small quantities it is 
believed that percentages would be misleading. 
The superior qualities of first-generation hybrids in maize as set 
forth by Collins may be summarized as follows: (1) Increased yield. (2) 
Uniformity equal to that of the parents. (3) Quality intermediate 
between parents (but Hayes’ data indicate complete dominance of low 
protein over high protein). (4) Increased immunity from disease. 
(5) Extension of the industry into new territory. Especially strong 
evidence for this is found in several of the crosses between diverse types. 
“ Almost without regard to the nature of the parents the hybrids remained 
dark green and vigorous when nearly all the pure strains were giving 
evidence of the lack of moisture by their curved leaves and yellow 
color.” (6) Less localization of highly bred strains. The importance 
of local adjustment in highly bred strains is the chief reason for the 
disappointment which sweet corn growers experience when they purchase 
carefully selected strains from other localities. ‘‘First-generation 
hybrids are to a great extent independent of this delicate adjustment to 
local conditions.” (7) Increased utilization of the work of experienced 
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