252 hmerson. 



and lacked a factor H wliich may be assumed to change waxy into 

 horny endosperm. Tlie wliite horny parent must have had H and may 

 liave lacked either one or both of the factors C and R, or its color- 

 lessness may have been due to the presence of a color inhibitor I. 

 The fact that the colorless condition was almost completely dominant 

 to the colored condition suggests the presence of I. 



An anomalous seed from such a cross, a seed colored and waxy 

 in part and wliite and horny in part, can be interpreted by hypothesis I, 

 independent development of the second male nucleus, without the 

 necessity of any assumption as to the possible dominant or recessive 

 nature of the aleurone color. Hypothesis II, independent development 

 of one polar nucleus and fusion of the second male nucleus with the 

 other polar nucleus, can be used to intei'pret the result, only if it be 

 assumed that an inhibitor of aleui-one color is present. Otherwise the 

 seed must have been colored throughout. Apparently something of the 

 nature of one or the other of these two hypotheses is expressed by 

 Collins (2) in the statement: "If we are to venture into this dangerous 

 field of speculation it seems more reasonable to think of the parental 

 gametes as l)eing imperfectly combined, the two parts of the seed falling 

 under the influence of different parents". 



Vegetative segregation, hypothesis 111, also serves well as an ex- 

 planation of this anomalous seed. If such segregation occurred, however, 

 it must have included at least two factors. If an inliibitor of color 

 were not concerned, both H and either C or R must have been included 

 in the segregation. Or again if 1 were present, the supposed segre- 

 gation must have included both I and H. It was shown that in the 

 other cases of anomalous endosperm reported here not more than one 

 of the two or more heterozygous factors present could have been con- 

 cerned in the segregation. In considering this contrast, it may be illu- 

 minating to recall that there is (Collins (Ij) a partial linkage— coupling, 

 correlation, allelomorphism, association, coherence or what not — between 

 aleurone color and waxy or horny endosperm. While the genetic factors 

 that are included in this linkage cannot now be stated exactly, the 

 evidence indicates that H is linked with either C or R. The fact that 

 colored aleurone occurred in about three times as many seeds as did 

 colorless aleurone shows that I was not present and therefore could 

 not have been concerned in the linkage. 



It was shown above that H and either C, R or I must have been 

 included in the vegetative segregation that is here supposed to have 



