Aug.6. I9I7 Studies on Oat Breeding 301 



hull-less type discussed above. The biflorous condition of flowers is 

 completely linked with firmly hulled kernals. In this respect the F2 

 generation segregates a group of plants which reproduce the type of the 

 Victor parent, as will be seen from Plate 43, A. The grain of this group, 

 except for the rather heavy pubescence at the base of the grain, resembles 

 very closely the type of grain of the Victor parent (PI. 46, B). 



Within the limits drawn by the above two groups of the parental type 

 there is a rather wide range of intermediate forms marked by different 

 gradations in regard to the hull character. Four types may be dis- 

 tinguished. Beginning with the group most nearly approaching the 

 naked condition of grain, there is a form in which a few upper kernels 

 in spikelets borne on the lowest whorl of the panicle are intermediately 

 or firmly hulled, all the others being naked. The next form stands 

 close to the former, but is marked by the presence of a few intermediately 

 hulled lower kernels in the spikelets in the lower region of the panicle. 



This form leads to the next type, which represents the largest group 

 among the intermediate plants and shows all possible gradations between 

 the naked and the hulled oat on the same panicle. Plate 45 shows a 

 series of spikelets with the different gradations of the hull character, 

 taken from a single oat head. The spikelets with the naked kernels are 

 borne on the upper portions of the whorl. Next to these appear spike- 

 lets in which the lowest kernel is naked, and the upper ones are inter- 

 mediately hulled. About the middle of the panicle spikelets prevail in 

 which the lowest kernel is naked and the upper kernels firmly hulled. 

 Below these, a condition is reached in which the lower kernel in the 

 spikelet is intermediately hulled and the upper kernels are firmly hulled. 

 Finally, at the base of the spikelet there are a few perfectly hulled 

 kernels. It will be noted that this group of intermediate plants resembles 

 the Fi generation more closely than any other form. 



The last group of the Fj plants with intermediately hulled grain link- 

 ing with the type of plants with firmly hulled grain shows a rather 

 simple condition in which the tip spikelets are hull-less, the grain in the 

 middle section of the panicle is intermediately hulled, while the lowest 

 part of the panicle bears only completely hulled grain. 



After the description of the F2 forms as to type of hull, the inherit- 

 ance of the hull character may now be discussed. As shown above, the 

 first -generation plants are intermediate, showing the characters of both 

 parents. The second generation segregates into two groups of the 

 parental types and into a group of intermediate forms presenting a 

 continuous series of different gradations. Whether these gradations 

 within the group of intermediate forms are controlled by separate 

 factors that will cause some of them to breed true or whether they are 

 to be considered as a result of the heterozygous condition with only 

 one pair of factors involved can not be determined at present. It is 

 hoped that the data for the third generation will throw light on this 



