Nov. 12, 1921 Genetic Behavior of Spelt Form in Crosses 355 



Ss and produced spelts and wheats in the 3 to i ratio. If these F3 

 heterozygous plants have all the same genotypic constitution with 

 regard to the spelt factor we would expect to see them produce similar 

 F3 spelt distributions. These distributions obtained experimentally are 

 far from being uniform. For instance, plant i326oa-3 (Table X) pro- 

 duced individuals mainly of classes 8 to 9, and plant i326oa-6 produced 

 its spelts in classes i and 2 only. The progeny of i326oa-i5, on the 

 other hand, showed no definite grouping, the curve spreading from one 

 extreme to the other. 



It may be argued that (i) these variations are insignificant; (2) they 

 may be due to variations in soil and other external conditions; or (3) they 

 are merely nonheritable fluctuations. 



These arguments may be answered easily: 



1 . In the first place, let us take the first two frequencies (classes i to 

 9, inclusive), namely, those of i326oa-3 and i326oa-6 (Table X). The 

 means are 8.00 ±0.29 and 1.3 1 ±0.08. The difference between the two 

 means is 6.69 ±0.30. This difference, it is seen, is very significant. 

 Similar striking differences will be found when the means of the other 

 distributions are compared. 



2. With regard to variations due to soil conditions and external factors, 

 it is only necessary to mention that these plants were grown on the same 

 plot of the experimental field. The pedigree numbers following the 

 family number represent the numbers of the rows in which the progeny 

 of each of the Fj plants was grown. For instance, the progenies of 

 plants i326oa-28, 29, 30 (at bottom of Table X) were grown in three 

 adjacent rows, yet i326oa-28 was composed of individuals contributing 

 to nearly all classes of spelting, i326oa-29 produced practically all typical 

 spelts, and the progeny of i326oa-30 were nearly all speltoid forms 

 approaching the wheat type. So this second objection may also be 

 dismissed. 



3. As to the nonheritability of these variations, the objection may be 

 settled by comparing the Fj and F3 generations in terms of the coefficient 

 of heredity. If these variations are nonheritable fluctuations, there 

 should be no correlation between the Fj and F3. Putting the statement 

 in the affirmative, if there is a significant correlation in the degree of 

 spelting of parent and offspring of the F2 and F3, then it is a direct and 

 indisputable proof that these variations are transmitted to the follow- 

 ing generations — that is, they are heritable. The accompanying corre- 

 lation table (Table XI) has been prepared with a view of determining the 

 validity of this last objection. The x-axis represents the mean classes 

 of the F3 and the y-axis represents the classes of the F2 individuals which 

 produced these Fg forms. In this table are included all the progeny of 

 the heterozygous forms of series 13255a and 13260a in order to have a 

 sufficient number of individuals. The coefficient of heredity as calculated 

 is 0.880 ±0.029. As this coefficient is over 0.5 and over 10 times its 



