No. 608] WEAK AWX IX .IT'EA^l CBOSSES 



489 



Discussion of Results in Weak-an u X Aicnless.— From 

 the data presented above, the following conclusions may- 

 be drawn as to the inheritance of awns in crosses between 

 the weak-awned and the awnless types of oats. 



The awnless type is almost completely dominant in the 

 first generation, only a few of the plants possessing awns 

 and those in small percentages. 



The second generation gives awnless, partially-awned 

 and fully-awned plants in a ratio which approximates 

 1:2:1. The totals of data from second generation plants 

 of series 2,501 and 514 are rea?onal)ly cfose to this ratio: 



The behavior of the fully-awned plants shows that this 

 type is the pure recessive, for it breeds true in all cases 

 from the second generation. 



All of the partially-awned plants proved to be 

 heterozygous, throwing in the third generation approxi- 

 mately three plants not fully awned to one fully-awned 

 plant. 



The awnless plants of the second generation were 

 found to comprise both homozygous plants of the parental 

 type and heterozj'gous intermediates which later broke up 

 in the same manner as the partially-awned Fo plants. It 

 might be expected that some of the awnless Fo plants 

 would prove to be heterozygous, since awnless plants are 

 found commonly in the first generation. 



From these results, it is apparent that w^e cannot cor- 

 rectly speak of the awnless oat as the dominant, type, nor 

 should we restrict the use of the term intermediates to 

 those plants which are ]>artially awned. 



It seems very probable that tlir- difference between the 

 weak-awned and the awnk'>s vai ioties of oats, at least in 

 the varieties studied, may be accounted for by the assump- 



