HYBRIDISATION AND WHEAT HYBRIDS 395 



dicoccum parent, I have no doubt, was a white-chaffed European form, 

 with empty glumes about 10 mm. long, terminating in a curved apical 

 tooth, and grain red and flinty, about 9 mm. long. 



The Fj ear was narrow, about 10 cm. long, with brittle rachis, white 

 awns, and empty glumes about 15 mm. long, clothed with fine, adpressed 

 hairs ; the grains were dark red, flinty, and 9-5 mm. long. 



The F 2 from this gave three clearly differentiated types, viz. : 



(1) T. polonicum, almost typical in form and size of ear, with some- 

 what brittle rachis, thin, quite glabrous, empty glumes, 25 mm. long, and 

 dark red flinty grain 10 mm. long. 



(2) A form closely resembling the white-chaffed European T. dicoccum, 

 with fragile rachis, stout empty glumes, finely pubescent, about n mm. 

 long, with a strong, incurved, apical tooth, and dark-red flinty grain : 

 some of the ears had fine black awns. 



(3) An intermediate type with brittle ears, nearer in character to the 

 dicoccum than the polonicum parent, the empty glumes quite glabrous, 

 intermediate in texture, and 15-17 mm. long, ending in an intermediate 

 incurved tooth, the grain 10 mm. long, dark red and flinty. 



The types (i) and (2) bred true in the F 3 and F 4 generations : type (3) 

 behaved as the Fj plant. The young leaves of all the plants were pubescent 

 like those of the dicoccum parent ; none were glabrous like polonicum. 

 Brittleness of ear and red grain were dominant, and the white grain of 

 the polonicum parent did not reappear in the F 2 or F 3 generations. 



(ii.) T. polonicum x T. dicoccum, var. Arraseita (" T. Eloboni"). This 

 hybrid obtained by Biffen in 1913 was investigated by Caporn later. 



The average glume-length of the polonicum parent was 29-23 mm., 

 the glume-length of the dicoccum parent ranging between 8 mm. and 

 13 mm. 



The F x plants had intermediate ears with glumes intermediate in size 

 and form between those of the parents. 



The grain was also intermediate in size, but purple like that of the 

 dicoccum parent. 



The F 2 generation showed indistinct 1:2:1 segregation, with the 

 glumes of the homozygous " long-glumed " plants 24-14 mm. long 

 somewhat shorter than those of the polonicum grandparent : those of the 

 homozygous " short-glumed " segregates being longer than those of the 

 corresponding dicoccum grandparent. 



c. T. polonicum x T. durum (Kubanka). A cross between these wheats 

 was made in 1912 by Backhouse. 



The average glume-length of the polonicum parent was 29 mm., that 

 of the durum parent 12 mm. The F x was intermediate, with glume- 

 length 18-19 mm. 



In F 2 w r ere long-glumed and intermediate-glumed plants, forming a 



