CLASSIFICATION AND INHERITANCE IN WHEAT 79 



concluding that the cultivated einmer and spelt groups arose 

 from different wild stem species. It is also essential to point out 

 that all crosses between the cultivated naked emmer wheats with 

 naked wheats belonging to the spelt group are not entirely fertile. 

 Indications of partial sterility are generally apparent if the results 

 are carefully analyzed (Kezer and Boyack, 1918) (Freeman, 1919) 

 (Hayes and others, 1920). 



Polonicum Crossed with Other Species. Crosses between 

 polonicum and other forms have been studied. Tschermak 

 (1913), in a cross between polonicum and vulgare, explained the 

 results by two main factor differences. The FI was of inter- 

 mediate glume length and in Fz polonicum, durum, and vulgare 

 forms were obtained as well as intermediates. Pure polonicum 

 was considered to contain two dominant factors in the homo- 

 zygous condition; durum, one dominant factor pair in the homo- 

 zygous condition; and the pure vulgare forms, both factors in 

 the recessive condition. 



Polonicum (Backhouse, 1918) crossed with durum or turgi- 

 dum gave intermediate glume length in FI and segregation in 

 F 2 in a ratio of 3 longs and intermediates to 1 short. Biffen 

 (1916) and Backhouse in separate studies considered the factor 

 for polonicum glume to inhibit chaff pubescence and color. In a 

 cross between durum (Kubanka) with a polonicum variety, the F% 

 segregated for glume length and hairy chaff. The short-glumed 

 plants were in a ratio of 3 hairy to 1 smooth, while the long- 

 glumed plants were difficult to classify for condition of chaff. 

 Crosses of different long-glumed plants with other wheats showed 

 that a part of these long-glumed wheats contained a genetic 

 factor for hairy chaff. Results were explained on the hypothesis 

 that the factor for long glume partially inhibited development 

 of hairy chaff. Similar results were obtained by Biffen (1916), 

 for inhibition of glume color by the polonicum factor for glume 

 length. 



Some Linkage Results in Wheat Crosses. In crosses be- 

 tween the different species some evidences of linkage have 

 been observed. In turgidum-vulgare crosses, Biffen (1905) ob- 

 tained complete linkage of gray color of glumes with hairy chaff. 

 Engledow (1914) crossed a black-glumed wheat obtained from a 

 turgidum-fife cross with a rough-chaffed, white-glumed variety, 

 Essex Rough Chaff. The ratio obtained in F z was explained on 

 the basis of repulsion between the factors for black glume color 



