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THE AMERICAN NATURALIST [Vol. LVI 



figures are based, tlie averages of the coefficients of vari- 

 ability of the Fi X Fi and the Fg families are brought 

 together in table 1. With these are given sonae figures 

 averaged from the Fi parents. These are not from the 

 exact first generation parents of the progenies used to 



TABLE I 



:tt of Single First Generation, Double 

 I Generation Hybrids 



give the other results in Table I. They are similar but 

 were not grown in the same years. They can not be 

 compared as closely to the F^ X Fj and F2 lots as these 

 can be compared with each other. The coefficients for 

 variability of the Fj X Fj and the F2 plants, averaged 

 from three diflPerent combinations with a fairly large 

 number of plants in each grown from seed of which the 

 two contrasted kinds came from the same ears, are strictly 

 comparable. The greater growth of the double hybrids 

 as shown by the increase of the means makes comparison 

 of the coefficients of variability somewhat unreliable. The 

 appearance of the plants in the field supports the statis- 

 tical data, as it is the uniform production which makes 

 the hybrid plants so valuable for agricultural purposes. 

 There is a noticeable difference between the double cross 

 and the self-fertilized second generation in even size, 

 similar appearance and general excellence as the plants 

 are harvested in the field. 



The figures show that the variability of the F^ X Fj, 

 families is about the same as the Fo families in rows of 

 grain and nodes per plant. In height of plant, length of 

 ear and weight of grain per plant, all characters which 



