'M^^L^^^Ai^B^Bic. 



HARVESTING THE WHEAT HYBRIDS 



The rest of the test includes only laboratory methods for this generation. (Fig. 12. 



plants in the second generation in the 

 ratio of 15 black to 1 non-black. 



Crosses between the hulled and naked 

 oats show that nakedness behaves as a 

 simple monohybrid, giving 1 naked, 2 

 intermediate to 1 hulled. However, 

 the intermediate forms show all grada- 

 tions of the naked condition. Some 

 will be nearly all of the naked type 

 while others will be nearly all of the 

 hulled type. These different hetero- 

 zygous types have been tested in 

 further generations and, while they 

 reproduce the 1:2:1 ratio, nevertheless, 

 they produce heterozygous forms which 

 differ as to the percentage of hulled 

 kernels. The percentage of hulled ker- 

 nels is high or low, depending on the 

 type of parent form chosen. Those 

 having a high amount of hulled repro- 

 duce this type. Thus, while the ratio 

 obtained in this cross is apparently a 

 simple one, there must be some modi- 

 fying factor or factors at work which 



influence the production of the hulled 

 or naked type. Fig. 13 shows the parent 

 forms and Fi types of some hulled and 

 hull -less crosses. 



Studies on awn inheritance show 

 that for the weak awn the fully awned 

 condition is recessive and the character 

 seems to follow a simple 1:2:1 ratio. 

 The liguleless types have been crossed 

 with a number of ligule bearing fonns. 

 So far the studies have shown that the 

 presence of ligule was represented by 1 

 and 2 factors in the different sorts. A 

 number of linkages have been foimd 

 to exist in oats as evidenced by a ntmiber 

 of the crosses studies. 



In the hybridization work with wheat 

 crosses have been made between the 

 different cultivated fonns as well as be- 

 tween the different wheat species. The 

 culti\'ated forms have also been crossed 

 with the various species and with the 

 wild form, T. hennonis.' Such char- 

 acters as color of chaff", color of kernel, 



*The name suggested by O. F. Cook, Bulletin 274, R. P. S. 

 72 



