HYBRIDISATION AND WHEAT HYBRIDS 403 



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

 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. compaction 3 

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

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



In F t 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 vulgart (Devon) with T. cumf>actum 

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

 intermediate Fj hybrid from T. eompactum (HcYisson) xa lax, long-eared 

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

 eared forms in the ratio i : 2 : i. 



vii. T. eompactum (Swedish Binkel) x T. vulgart. The crossing of 

 T. eompactum with T. vulgare was extensively studied by Nilsson-Khle, 

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

 three long, lax-eared forms of 7'. vulgare. 



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

 eompactum parent, resembling an ordinary " Squarehead." In F, 

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

 from a group of " Squarehead " hetero/ygotes and homozygous corn- 

 pa ft urns, 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 s were of the ordinary monohybrid type, viz. : 



i eompactum : 2 Squareheads : i Long-cared. 



The same variety of 7'. eompactum 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 

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

 being visible between the eompaetums and mm-compactums. 



In one example of the cross Binkel Pudel (Squarehead), the I-'., 

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

 parent ; 5 compactum-Yike plants and 28 ntm-eompaetums, chiefly very 

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



