UTILIZATION OF HYBRIDS IN PLANT BREEDING 361 
seed could have no advantage in this case. The ear produced 212 white, 
or pure, seeds and 161 that were yellow, or hybrid. The average weight 
of the pure seed was 283 gm. per 1000 kernels. The average weight of 
the hybrid seed was 292.5 gm. per 1000, a difference of 9.5 + 1.06 gm., 
or 3.4 per cent.’’? In the experiment itself eleven ears, involving five 
different varieties, were crossed, giving a total of 1,658 hybrid seeds to be 
compared with 3,513 selfed or pure seeds. In every instance the size of 
the seed was materially increased by the foreign pollen, the increase 
ranging from 2.8 to 21.1 per cent. The fact that the pericarp of the 
mother plant is not strictly a part of the seed but is of purely maternal 
origin might seem difficult to harmonize with the results, but Collins 
and Kempton point out that the necessary increase in size of the pericarp 
would be comparatively slight and to seek any explanation may be 
superfluous. The practical value of this evidence is great. As the 
authors state, ‘‘the results afford additional reason for the use of first 
generation hybrid seed; but even where hybrid seed is not to be used, 
the planting of two varieties in alternate rows may be found to increase 
the yields sufficiently to warrant the additional trouble.” And further, 
“as the increased size is evidently a manifestation of vigor, it may be 
considered as a factor of adaptation, like the vigor of the first-generation 
hybrid plants. It would seem especially desirable to take advaritage of 
this method of increasing yield in regions which do not produce their own 
seed corn.”’ 
Centralized Seed Corn Production.—Carefully selected strains of 
maize are liable to prove disappointing when grown under conditions 
different from those obtaining at the locations where they are produced. 
But the work of intensive selection requires considerable skill and ex- 
perience and the farmer can seldom attend to it properly. He should 
obtain his selected seed corn from a local breeder if possible. The fact 
that F, hybrids in maize are comparatively resistant to local and seasonal 
conditions which prove detrimental to pure strains indicates that such 
hybrids may be produced at central points in quite a large territory. 
When it is known which combination of varieties, or of pure strains of 
a single variety, is best adapted in certain localities, pure seed of these 
varieties or strains may be maintained and the crosses made under 
expert supervision at a central seed farm. On the other hand, a farmer 
who wishes to produce his own hybrid seed need not hesitate on account 
of increased cost of production. Collins has shown that even though the 
cost of raising hybrid seed be double that of ordinary seed, yet ‘‘ where 
increases ranging from 5 to 50 per cent. may be expected there are few 
farm operations that yield such large returns.” 
A Method of Producing Hybrid Corn Seed.—A grower intending 
to produce his own hybrid seed each year might do well by beginning 
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