HYBRIDISATION AND WHEAT HYBRIDS 375 



In addition to " Pudel " wheat, Nilsson-Ehle found that the grain 

 colour of Svaldf " Grenadier " wheat is a three-factor red. 



Investigations showed that the grain tints of Extra Squarehead II., 

 " Bore " wheat, and a pure line of Swedish T. compactum are two-factor 

 reds, hybrids of these with white-grained wheats segregating in F 2 in the 

 ratio 15 red : i white. 



A. and G. Howard obtained similar evidence of the existence of double 

 factors for red grain colour in some Indian forms of T. vulgare and of a 

 three-factor red in T. compactum, var. erinaceum (" American Club "). 



iv. Purple x White. Caporn studied the inheritance of the purple 

 tint in a cross made originally by Biffen between T. polonicum with white 

 translucent grain and the purple-grained Abyssinian wheat " T. Eloboni " 

 ( = T. dicoccum, var. Arraseita (p. 195)). 



The F x grains were all uniformly purple. In F 2 were found 

 (i) fully tinted or " flushed " grains of light and dark shades, (2) 

 grains with longitudinal streaks of purple, and (3) uncoloured grains 

 the proportions approximating to the ratio 3 flushed : i streaked : 12 

 uncoloured. 



Some of the ".streaked " plants bred true while others were hetero- 

 zygous " streakeds " whose descendants exhibited the simple 3 : i mono- 

 hybrid segregation. 



The " uncoloured " plants appeared to be of two kinds, namely (a) 

 those throwing " uncoloured " plants only, and (b) others giving " un- 

 coloured " and " streaked " progeny, the approximate ratio of a : b being 

 15 : i. 



Segregation similar to that occurring in F 2 was not found in F 3 ; other 

 complicated results requiring further study for elucidation were met with 

 in the F 3 generation. 



FLINTY AND MEALY ENDOSPERM. The inheritance of these characters 

 is complicated by the fact that their appearance is largely dependent upon 

 external conditions of soil and climate. 



The flinty character is stated by Biffen and Tschermak to be dominant, 

 but further investigation of the matter is desirable. 



SUSCEPTIBILITY AND RESISTANCE TO THE ATTACKS OF RUST-FUNGI 

 (Puccinia sp.). The variable incidence of the attacks of Yellow Rust 

 (Puccinia glumarum, Er. et Henn.) is strikingly evident almost every year 

 on examining the collection of wheats at Reading in spring. 



Upon T. aegilopoides and T. monococcum the rust is never found, and 

 several forms of T. dicoccoides, T. dicoccum, T. durum, T. turgidum, and 

 T. vulgare are usually nearly free from the parasite. A larger number 

 of forms of the same races are slightly attacked, while many forms of 

 T. vulgare, especially those from India, Persia, and Central Asia, are so 



