ture tended to increase the number of rows generally in the former 

 instance or to decrease them generally in the latter. Not the least 

 significant contrast therefore between the two self-fertilized strains 

 above described is that which deals with the number of rows of 

 grains on the ears. In the case of the selection to 14 rows, the result 

 shows a considerable predominance of 14 among the ears of this 

 year's (1907) crop, nearly 40 per cent falling into that single class 

 as compared with 38 per cent in the same class among the unselected 

 population with which the experiments were begun four years ago. 

 As 14 rows was the original prevailing class or "modal" class as 

 it is called, it is quite what we would expect, to find that continued 

 selection of this modal number has simply increased the relative 

 value of class 14. In the case of selection to 12 rows on the other 

 hand we are met with a surprise, for instead of the average number 

 of rows being between 12 and 14 as the supposition that we are 

 dealing with the fluctuations of a single elementary species whose 

 normal mode is 14 rows, would lead us to expect on theoretical 

 grounds, we find the prevailing class to be 10, with nearly 39 per 

 cent in that class. Knowing that this row was the result of con- 

 tinued selection of 12-rowed ears, one would infer from the v data 

 of this year's crop that the original condition of the population 

 the normal condition for the race to which this row belongs is 

 probably 10 rows or possibly even 8 rows as "the modal class, instead 

 of the 14 rows possessed by the original stock from which all my 

 cultures came. It is demonstrated therefore that these two rows 

 belong to distinct races or elementary species of corn, though the 

 original stock appeared to be fairly homogeneous. Most of the 

 other self-fertilized rows showed by various marks that they were 

 likewise to be considered members of distinct biotypes, instead of 

 fluctuant parts of a single biotype as I believed they were when 

 I began my investigation. 



The obvious conclusion to be reached is that an ordinary corn- 

 field is a series of very complex hybrids produced by the combination 

 of numerous elementary species. Self-fertilization soon eliminates 

 the hybrid elements and reduces the strain to its elementary com- 

 ponents. In the comparison between a self-fertilized strain and a 

 cross-fertilized strain of the same origin, we are not dealing, then, 

 with the effects of cross and self-fertilization as such, but with the 

 relative vigor of biotypes and their hybirds. The greater vigor 

 of the cross-fertilized rows is thus immediately brought into harmony 

 with the almost universal observation that hybrids between nearly 

 related forms are more vigorous than either parent. 



The components of a hybrid strain may be separated by means 

 of cross-fertilization just as surely as by self-fertilization, if the 

 parents of the cross are rigidly selected, generation after generation, 

 for definite characteristics; but the process of segregation will be 

 in this case much slower, because in each cross some of the elements 

 which were eliminated from the mother will be reintroduced by the 



