IQII] CURRENT LITERATURE 483 



while twenty corresponding F 2 families had an average height of 23.42 dm. 

 and gave a yield of only 44 . 62 bushels per acre. 



HAYES and EAST" have also shown a similar relation between first and 

 second generation crosses, one such cross giving 105.5 bushels per acre in F t 

 and only 51.5 bushels in F 2 , another cross giving respectively 117.5 bushels 

 per acre and 98 . 4 bushels per acre. These authors give a good discussion of 

 the economic bearings of these results and methods of putting them to practical 

 use. 



COLLINS^ has also shown the practical value of hybridization methods in 

 corn growing, reporting on the results of sixteen rather wide crosses, all but two 

 of which gave higher yields than the average of the parents, and all but four 

 exceeding the better parent in yielding capacity. PEARL and SURFACE/* 

 while subscribing to the correctness of the genotype idea as applied to maize, 

 are of the opinion that the ordinary ear-to-the-row selection method "in a 

 much cruder and less precise way, really makes use of the same principle" as 

 the reviewer's "pure-line method," and they advocate simply the relaxation of 

 the selection after a few years, by which time the "more strikingly undesirable 

 genotypes will have been automatically eliminated." This view fails to take 

 account of the relatively greater vigor in the F x hybrids. EAST, Z S HAYES and 

 EAST, 16 and COLLINS, I7 on the other hand, urge the use of the method of 

 MORROW and GARDNER, l8 as the most practical means of utilizing the greater 

 vigor produced by heterozygosis, and the reviewer believes that the attitude 

 of these authors is justifiable. The method of MORROW and GARDNER is 

 identical with the "pure-line" method, except that highly developed commer- 

 cial varieties are used in the place of pure self-fertilized strains. The two 

 chosen parental types are grown in alternate rows in an isolated plot, and one 

 variety is detasseled. The seed for the general crop is harvested from the 

 detasseled row, and the process is repeated year after year, using the same 

 parental varieties. 



EAST and HAYES 19 have made a most important contribution to knowledge 



12 HAYES, H. K., and EAST, E. M., Improvement in corn. Bull. Conn. Agr. 

 Exp. Sta. pp. 21. pis. 4. 1911. 



13 COLLINS, G. N., The value of first-generation hybrids in corn. Bull. 191, B.P.I., 

 U.S. Dept. Agr. pp. 45. 1910. 



* PEARL, R., and SURFACE, F. M., Experiments in breeding sweet corn. Ann. 

 Rep. Maine Agr. Exp. Sta. 1910. pp. 249-307. Bull. 183. figs. 220-233. 



T EAST, E. M., The distinction between development and heredity in inbreeding. 

 Amer. Nat. 43:173-181. 1909. 



16 Op. dt. ^ Op. cit. 



18 MORROW, G. E., and GARDNER, F. D., Field experiments with corn 1892. 

 Bull. 25, 111. Agr. Exp. Sta. pp. 173-203. 1893. 



J 9 EAST, E. M., and HAYES, H. K., Inheritance in maize. Bull. Conn. Agr. Exp. 

 Sta. pp. 137. pis. 25. 1911. 



