HYBRIDISATION AND WHEAT HYBRIDS 403 



From one of the bearded Squareheads (c) were obtained in F 3 u 

 bearded glabrous and 35 beardless glabrous Squareheads 



= Bearded, i : Beardless, 3. 



Another gave 15 bearded Squareheads, 58 beardless Squareheads, and 

 2 lax-eared, beardless plants. 



Bearded, i : Beardless, 4. 



vi. T. vulgare 9 (Velvet Kolben, Beardless) x T. compactum $ 

 (Velvet Igel, Bearded). The F x of this cross obtained by Riimker was 

 of intermediate ear-density with white velvet chaff and beardless ears. 



In F 2 appeared plants with bearded and beardless ears, some long 

 and lax, others of intermediate length and denser, though none were of 

 the " Squarehead " type. Although both grandparents were velvet- 

 chaffed, glabrous-glumed forms appeared in this generation. 



Ratios : Velvet-chaffed, 3 : Glabrous, i. Bearded, 5 : Beardless, 101. 



Biffen crossed a long-eared vulgare (Devon) with T. compactum 

 (Hedgehog) and found the F x intermediate. Strampelli also obtained an 

 intermediate F x hybrid from T. compactum (Herisson) x a lax, long-eared 

 T. vulgare (Rieti), the F 2 giving compactums, intermediates, and long- 

 eared forms in the ratio 1:2:1. 



vii. T. compactum (Swedish Binkel) x T. vulgare, The crossing of 

 T. compactum with T. vulgare was extensively studied by Nilsson-Ehle, 

 who crossed Swedish Binkel, an old beardless form of T. compactum, with 

 three long, lax-eared forms of T. vulgare. 



The Fj plants had ears somewhat longer and laxer than those of the 

 compactum parent; resembling an ordinary " Squarehead." In F 2 

 appeared long, lax-eared, homozygous, recessive forms sharply separated 

 from a group of " Squarehead " heterozygotes and homozygous com- 

 pactums, the two latter not always clearly differentiated from each other, 

 but whose genetic constitution was revealed in the F 3 generation. 



The ratios of the F 2 were of the ordinary monohybrid type, viz. : 



i compactum : 2 Squareheads : i Long-eared. 



The same variety of T. compactum was also crossed with " Pudel " 

 and " Bore " wheats comparatively dense-eared " Squarehead " forms 

 of T. vulgare. 



The F! of these crosses was dense-eared, closely resembling the 

 compactum parent. Segregation in F 2 was complex, no sharp distinction 

 being visible between the compactums and non-compactums. 



In one example of the cross Binkel x Pudel (Squarehead), the F 2 

 consisted of 61 compactums, 5 of them denser than the " Binkel " grand- 

 parent ; 5 compactum-\\ke plants and 28 non-compactums, chiefly very 

 lax-eared, only two being as dense as the Pudel grandparent. 



