3o6 



Journal of Agricultural Research 



Vol. X, No. 6 



Table VII. — Relation of the color genes and the length of pubescence 



On returning to the question of the presence and absence of pubescence 

 at the base of the lower grain, several interesting features may be noted. 

 As already stated, the grain of the Victor parent shows a few long hairs 

 at the base of the lower grain. In the first generation this pubescence is 

 intensified, and in the second generation many plants show thick, long 

 tufts at the side of the base. The difference in the pubescence of the grain 

 of the parent plant and these second-generation plants can easily be seen 

 by comparing figures A and B of Plate 46. 



The F2 generation thus presents an augmentation of the pubescence. 

 The pubescence appears here not only intensified but also as a dihybrid 

 character. The mere intensifying of the pubescence may conceivably be 

 due to the stimulating influence of hybridization. It is further possible 

 that the augmentation of the pubescence and its dihybrid character is 

 accounted for by the hulled Victor parents' bearing latent characters 

 which through hybridization become activated and released. 



A more plausible and simple explanation of the bifactorial character of 

 the pubescence in the second generation is suggested by the assumption 

 of a second gene for pubescence entering from the naked parent. The 

 question whether the naked parent contributed a gene for pubescence in 

 the hybrid progeny can not be solved directly, since, owing to the naked- 

 ness of the grain, the manifestation of a possible inherent gene for pubes- 

 cence is prevented. However, the evidence obtained in other crosses 

 between the hulled Victor oat used in the present cross and other hulled 

 strains tends to indicate that the pubescence of the Victor oat is a mono- 

 hybrid character. This evidence then speaks in favor of the assumption 

 in the present cross of a gene for pubescence in the naked parent. 



A still more remarkable feature of this cross is the presence of a pubes- 

 cence of a distinct type at the base of the upper grain in the hybrid 

 plants (PI. 46, B; 47). While several cultivated oat varieties have been 

 observed which possess a pubescence of varying strength at the base of 

 the lower grain, only three cases are recorded in the literature in which 

 a few individual spikelets developed pubescence also at the base of the 

 upper grain. Thus, Christie (2) records a case of two Danish varieties 

 developing a pubescence at the base of the upper grain. Nilsson-Ehle 

 (5) found that certain plants which he regards as atavistic regressions 



