304 Journal of Agricultural Research voi.x, no. 6 



the free expression of the genes for pubescence at the base of the lower 

 grain if present. In the present data there are 323 Fg plants which 

 fulfill these conditions. They include all the plants with completely- 

 hulled grain and those intermediate forms which most closely approach 

 this condition. Of these plants 300 are pubescent and 23 are smooth 

 (PI. 42, B). These numbers indicate a bifactorial character. Calcu- 

 lating the expected number of plants on the 15-to-i ratio, we have the 

 results shown in Table V. 



The agreement here is very good. 



It should not be forgotten, however, that these results are obtained 

 from a selected population. In such a case there is always the danger 

 that, through linkage or for other reasons, the selected group may not 

 represent the condition in the whole population. However, a considera- 

 tion of all the forms of the second generation that have an opportunity 

 for the expression of the genes for pubescence furnishes evidence that 

 the group of plants discussed above does represent a random sample of 

 the Fg population. Of the whole Fj population 229 plants have com- 

 pletely naked grain. It is obvious that these plants must be excluded 

 from a consideration of the character of pubescence. Of the remaining 

 625 plants, 369 are pubescent at the base of the lower grain, 128 are 

 pubescent at the base of both lower and upper grain, 81 are pubescent 

 at the base of the upper grain only, and 47 are smooth. The group of 81 

 plants pubescent only at the base of the upper grain presents a very 

 interesting condition which is the result of the interference of the naked- 

 ness or seminakedness of the lower grain with the manifestation of the 

 pubescence at its base. 



While this case will be more fully discussed in connection with the 

 discussion of the pubescence of the upper grain, it may suffice here to 

 state that in all the 81 plants the lower grain was totally or partly naked, 

 and that this condition obviously prevented the development of pubes- 

 cence at the base of the lower grain. This circumstance, coupled with 

 the fact that heretofore not a single case has been reported of an oat, 

 cultivated or wild, with the lower grain smooth and the upper pubescent, 

 justifies the conclusion that the 81 plants might have developed the 

 pubescence at the base of the lower grain if it were not for its naked or 



