HOWARD AND HOWARD. 33 



The distinction between the above two kinds of inheritance 

 in bearding is of great interest. In one case the simple Mendelian 

 scheme is followed, but there is no question of dominance in the Fj 

 which is clearly intermediate. In all these cases however one of the 

 parents is only beardless in the ordinary sense of the term, short 

 tips to the glumes being present. In the other case the F x is almost 

 beardless while in the F 2 the 15:1 ratio is obtained when all plants 

 with beards, whatever may be their length, are separated from the 

 absolutely beardless ones. Here, however, one of the parents is ab- 

 solutely beardless. 



In the following crosses the same bearded parent (American 

 Club) occurs in both classes — 



(1) American Club (bearded) x Pusa 6 (beardless) with the 



1:2:1 ratio in the F 2 . 



(2) American Club (bearded) x Pusa 4 (beardless) gave the 



15 : 1 ratio in the F 2 . 



Pusa 6 has short tips to the awns while Pusa 4 is absolutely beard- 

 less. This appears to indicate that in American Club two factors 

 are present, a long and short factor, while both are absent in Pusa 4 

 and only the short factor is present in Pusa 6. 



Before discussing the possible explanations of these phenomena 

 the results of the other crosses made with bearded parents must be 

 stated. In crosses between plants with slight tips to the awns and 

 absolutely beardless parents the Fj generation was intermediate 

 and the F 2 gave fully tipped, intermediate and absolutely beardless 

 plants in the ratio 1:2:1 and no difficulty was experienced in making 

 the separation. Crosses between fully bearded parents gave similar 

 offspring in the F x and again in the F 2 . In crosses between tipped 

 parents the Fx and F 2 generations were alike and resembled the parents 

 in having all the awns with tips of similar length. These results 

 are given in the following table : — 



