Nov. ra, igar Gefietic BehavloY of spelt Form in Crosses 361 



100 to I, with some sets of crosses producing no spelt at all. Besides 

 the true spelts, a number of speltoid forms also segregated. 



The absence of the spelt type in the F^ generation shows that the 

 absence of the spelt character in one of the parents was due to the pres- 

 ence of an inhibitor in the parent plant which carried the S factor. If 

 the appearance of the spelt form in the Fj generation was due to com- 

 plementary factors furnished by both parents, the spelt should have 

 appeared in the F^ generation. Such was not the case. 



The cultures consisted of over a thousand Fg plants. It is not now 

 absolutely necessary to know how, or exactly in what proportion, these 

 appeared. The purpose of citing these examples is to substantiate the 

 views expressed above regarding the possibilities of producing synthetic 

 spelts from wheat X wheat crosses, which might have been regarded 

 as a mere speculation in the absence of this experimental evidence. 

 The fact that there were no spelts grown near the P^ or F^ plants and 

 that spelts appeared in more than one cross excludes the possibility of 

 accidental or natural cross-fertilization. 



These observations show that common wheats may carry the spelt 

 factor, but the latter can not express itself because one or more diluting 

 or inhibiting factors are carried with it. Some of these diluting factors 

 may be regarded as inhibiting factors which are not totally dominant 

 but produce intermediacy in a heterozygous state. 



From the small percentage of spelts which appeared in the Fj genera- 

 tion in some cases, it may be inferred that there is one and in some 

 cases more diluting factors.^ 



The production of synthetic spelts in wheat X wheat crosses just con- 

 sidered is similar to the synthetic production of T. dicoccum dicoccoides, 

 the so-called "Wild Wheat" of Palestine, in the vulgar e X durum cross 

 (6). The wild character, consisting of a number of interdependent 

 specific characters, is strongly dominant over both the sativum and the 

 durum types, as is the spelt type toward sativum. Yet in both instances 

 the character showing strong dominance toward either of the parental 

 forms was carried by one of the parents together with a factor inhibiting 

 in one case the wild and in the other case the spelt characters. 



MODIFICATIONS OF MENDELIAN RATIOS 



The question of modifiers whose presence in the production of the 

 spelt character was demonstrated in various ways brings us to the con- 

 sideration of the modifications of mendelian ratios. As all spelts or all 

 wheats are not alike with respect to their ability to intensify, repress, 

 or inhibit the production of the spelt characters, it is natural to expect 



' Nilsson-Ehle (.8, q) and Kajanus (j, 4) have also observed the occurrence of spelts in certain sativum X 

 sativum crosses. They support the correctness of the foregoing observations and tend to preclude the 

 assumption of the possibility of the occurrence of some accidental or natural crossing of one of the sativum 

 patents with a spelt. 



