No. 60S] WEAK AWN IN AVENA CBOSSES 487 



with the fully-awned plants, we find that the separate 

 ratios closely approximate a 3 : 1 ratio. The ratio for all 

 six plants is 2.97 : 1.03, and its deviation is practically the 

 same as its probable error. 



TABLE V 



It is apparent from these data that the Fo grouping used 

 here includes in the awnless class certain individuals 

 which are heterozygous for awning, and which really 

 belong with the partially-awned plants. According to 

 Nilsson-Ehle (1914) environmental conditions have an 

 etfect upon the production of awns. It is quite possible 

 that the failure of tlie^c six: ]»lants to ])roduce some awns 

 is due to undetoniiiiicd eTiviiomiu^iitnl factors. 



A comparison of the relative iiuiiibcrs of awnless and 

 partially-awned })lants in Tables I \' and \' would seem to 

 indicate that awnless Fo plants tend to uive a higher per- 

 centage of awnless plants in F,, than <h> the jnirtially- 

 awned plants. This may be explained, however, by the 



