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



appears in the Fj generation, ranging from the true spelt to the typical 

 wheat form. In the segregates, a plant which has the glume form of 

 the spelt invariably has a brittle rachis and a nonshattering habit. If 

 the glume form is intermediate, the brittleness and shattering qualities 

 also are intermediate These three characters do not segregate inde- 

 pendently. A plant with sativum glumes, for instance, has not been 

 found whose rachis is brittle (a characteristic of the spelt only), nor 

 have we obtained a spelt-glumed plant which has as tenacious a rachis 

 as that of T. sativum. These species may present other characters, 

 such as pubescence, beardedness, glume color, etc. These are common 

 to both and segregate independently irrespective of the species. The 

 presence of correlation between some of these specific characters in 

 sativum X spelta crosses also has been noted by von Tschermak (12). 



Unless the linkage is absolute it does not exclude the possibility of 

 the occurrence of crossovers, but if crossing over ever occurs with respect 

 to these characters it must be very rare. 



The linkage of specific characters of spelt is very similar to the linkage 

 of a number of glume characters of the wild oats in crosses between wild 

 and cultivated forms described by Surface (u) and by Love and Craig (5), 



It is absolutely necessary to bear in mind that the determination of the 

 species is based only upon the presence, intensity of development, or 

 absence of the specific characters (glume characters, brittleness of rachis, 

 and seed-holding habit) , all of which are linked to a very large extent. 

 These characters show no independent segregation. It is obvious, 

 therefore, that they do not mendelize independently. The characters 

 which do segregate independently, such as pubescence, beardedness, 

 glume color, etc., are not taken into consideration.^ 



METHOD OF CLASSIFYING THE FORMS 



The second and subsequent filial generations of spelta X sativum crosses 

 show numerous gradations between the two parental forms. Some of 

 the F2 plants produced a progeny consisting of individuals which were 

 decidedly spelts, while others produced a progeny which, while all spelts, 

 yet resembled T. sativum to some extent and were distinctly different 

 from the former group of plants where all the individuals were markedly 

 spelt-like. 



Ten arbitrary classes were made in order to record the degree of in- 

 heritance of spelt characters. The typical or intense spelt which ex- 

 hibited all the specific spelt characters in their extreme forms was graded 

 I. As the exhibition of the intensity of these characters diminished — 

 that is, as they tended to approach those of the wheat — ^the heads were 



' Even these independently segregating characters vary in intensity and quality in these two species 

 when segregating in crosses. 



