stout: pollinations in cichorium intybus 421 



condition which is well shown by the numerous and well-known 

 results of the so-called ear-to-row tests. 



Further breeding work has shown that there are exceptions to 

 the general rule that crossing between varieties of corn gives an 

 Fi with greater vigor than that of either parent and further that 

 the yield may even be less than that of either parent (Hayes, '14, 

 p. 364). Collins ('14) points out that in corn "some crosses give 

 favorable results and others give little or no increase over the 

 yield of parents" (p. 91), and that there is a decidedly "abnormal 

 behavior of self-pollinated maize plants" with also wide individual 

 diversity in the yield of hybrids which make the satisfactory com- 

 parison of the yield of parents and hybrids difficult. 



It must be recognized that it has not been fully shown that in 

 corn the cross-pollination of plants of a good strain in such a manner 

 as to eliminate the effects of proterandry does not continue the 

 strain in inbreeding with high vigor and production. The condi- 

 tions in corn hardly make the tests as adequate as in tobacco, 

 but, considering all the data at their full value with proper con- 

 sideration of the limiting conditions, the results, as pointed out 

 by Burck for Darwin's data, can be interpreted as not at all in- 

 consistent with the view that the best development and fertility 

 is associated with greatest similarity. 



The emphasis that East and Hayes place on nuclear organization 

 in respect to presence or absence, or the presence of heterozygous 

 allelomorphs of assumed hereditary units is based largely on the 

 older conceptions that such units adequately represent characters 

 and segregate with purity in sporogenesis; both conceptions are 

 known not to be law^s as these authors evidently realize ('11, p. 42). 

 The marked increase in vigor which hybrids often show, especially 

 when there is also fertility, may very well involve elements of 

 similarity that pertain to a type of cell organization and sex 

 differentiation that is far more fundamental than differences or 

 similarities in purely nuclear organization such as may exist be- 

 tween varieties of the same species and such crosses may very 

 well restore in increased degree a type of ancestral cell organization 

 in much the manner that Burck has emphasized. 



The evidence obtained in animal-breeding, in which inbreeding 

 of pedigreed lines of descent is the nearest possible approach to 

 self-fertilization of nearly homozygous plants, has been variously 



