RESULTS WITH HYBRIDIZATION 115 



ISOLATING HIGH-YIELDING BIOTYPES 



84. Evidence at present indicates that high-yielding 

 ears, found by the ear-row method of testing, are in many 

 cases natural hybrids of high-yielding biotypes. Thus 

 by sectiring high-yielding ear remnants as foundation 

 stock, they might be inbred until pure types were ob- 

 tained. There is greater probability of securing biotypes 

 that would combine to advantage from this stock than if 

 a chance stock were used as a beginning. 



SUMMARY 



85. Fertilization is the result of the union of the con- 

 tents of a pollen grain with the egg cell of an ovary. 

 Xenia is the immediate effect of pollen in changing the 

 character of the maize grain. 



Mendel's law refers to the phenomenon of transmitting 

 characters in toto, without blending, as in the case of 

 dent and sweet corn when crossed. 



Hybridization usually gives a decided stimulus to growth, 

 while self-fertilization has the opposite effect. Continuous 

 self-fertilization may reduce yield to one-fourth or less 

 of the original yield, but the yield is fully restored in the 

 first generation hybrids. A field of corn appears to be a 

 miscellaneous mixture of biotypes, naturally not very 

 productive, but stimulated to the highest degree of pro- 

 ductivity by hybridizing. Certain biotypes hybridize 

 to better advantage than do others. 



^ References on xenia : — 

 Webber, H. J. (1900.) Xenia. U. S. Dept. Agr., Div. Veg. 



Physiol, and Path., Bui. 22. 

 GuiGNAED, L. (1901.) La Double Fecundation dans le Mais. 



Journ. Bot. [Paris], IB : 1-14. No. 2. 



