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 advantage 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 FI 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 



