14 



THE AMERICAN NATUBALIST 



[Vol. LIII 



ent which affected the heterozygous forms in such a way 

 as to modify the amount of hulled or hull-less kernels 

 present. 



In order to determine this effect in a more definite way 

 it was planned to sow seed from heterozygous individuals 

 which differed as to the percentage of hulled kernels 

 present. A rather large number of such seeds were 

 planted in 1915. The plants were severely injured by a 

 storm, so that accurate percentage determinations could 

 not be made. 



In the meantime, however, a number of other crosses 

 had been made in which the Avena nuda was used as one 

 parent. The following sorts were crossed with the naked 

 oats : Swedish Select, Sixty Day and Avena fatua. Other 

 crosses are being studied but these will be reported on 

 later. 



As regards the hull-less character the individuals 

 of these crosses were all similar to the description of the 

 first generation given earlier in this paper. Eegarding 

 the other characters, the cross between the hull-less form 

 and Avena fatua showed some very interesting varia- 

 tions. These will not now be discussed. 



Seeds of these various Fi plants were sown and the 

 resulting plants harvested. From each plant a head was 

 saved and threshed separately by hand and the plants 

 then sorted into hulled, intermediate and hull-less. The 

 result of the several crosses is given here : 



The probable error is +7.98 and the observed num- 

 bers agree fairly well with the expected numbers. The 

 number of hull-less plants is too low and the number of 

 intermediates too high. It is possible that in some cases 



