362 Journal of Agricultural Research voi. xxii. no. 7 



certain modifications of the 3 to i ratio. For instance, in certain spelt X 

 wheat crosses, depending upon the potency of the diluting factors, the 

 proportion of wheats to spelts may increase in certain amounts. In 

 some instances, the increase of wheats will be slight, so that the obtained 

 deviation from the 3 to i ratio, which will be on the side of excess for 

 the wheat class, will be considered within or near the limits of the probable 

 error and the inheritance will be regarded as simple mendelian. Perhaps 

 series 13255a, where an increased proportion of both constant breeding 

 wheats and F3 wheat segregates of heterozygous Fj plants are obtained, 

 represents such a case. 



It also is possible that the ratio may fall between 3 to i and i to i in 

 case the diluting factor is very strong. Here, then, will be an excess 

 in the homozygous wheat class at the expense of the homozygous dom- 

 inant spelt class. If factors of both dilution and of intensification 

 are introduced in the same cross, the experimental ratios will defy any 

 attempt at simple factorial explanations. The writers have obtained a 

 cross where the Fg generation suggested a possible 3 to i segregation, 

 but on examining the F3 generation, which was composed of a fairly 

 large population, neither the individual segregations nor the totals of 

 .these approached in any way 3 to i or i to 2 to i expectations. 



It naturally follows from the foregoing discussion that in spelt-wheat 

 crosses wide departures from simple ratios occasionally may be expected. 



SUMMARY 



T. spelta and T. sativum are differentiated by a number of linked 

 specific characters, which are present in one species and absent in the 

 other. These characters, so far as observed, are not inherited independ- 

 ently but are transmitted as a group. 



In crosses between a spelt and common wheats the F^ hybrid shows 

 dominance of the spelt, but this character appears in a somewhat diluted 

 form. In the second generation all classes of spelt inheritance are ob- 

 tained. In order to classify these forms, 10 arbitrary classes were 

 erected, class i representing the true spelt and class 10 the total absence 

 of this character. The intermediate classes represent diff'erent grades of 

 spelt inheritance. 



In most of the material studied there was but one factor difference for 

 spelt, but in two cases two spelt factors were present. Both 3 to i and 

 15 to I ratios were obtained. These ratios were verified after determin- 

 ing the genotypic constitution of the Fj plants, which gave pure breeding 

 spelts, inconstant spelts, and pure breeding wheats in the ratios of 

 I to 2 to I and 7 to 8 to i , respectively. Of the constant spelts produced 

 in crosses with this latter ratio, approximately half yielded (in the F3 

 generation) spelts and wheats in the ratio of 15 to i and the other half 

 in the ratio of 3 to i, as expected on the two factor hypothesis. 



