112 A MANUAL OF MENDELISM 



in every variety of colour, and frequently the lighter 

 shades of a darker colour may not be readily distin- 

 guishable from the darker shades of a lighter. 



So many colours indicate several colour factors with 

 several shade factors in addition, and the possibility of 

 the same colour getting one name from one observer 

 and another name from another is evident. 



Professor Nilsson-Ehle crossed a number of " black " 

 oats with white and found the hybrids to be browns of 

 several different shades. This indicated either more 

 than one pair of characters or intermediates between 

 blacks and whites. The hybrids' progeny were still 

 more diverse, but the blacks and browns of all shades 

 were counted together as one kind, and it was found 

 that, on the whole, they were to the whites in the ratio 

 3:1. Thus " black " was read dominant to white. 



A white variety, No. 0353, was crossed with two black 

 varieties, Nos. 0401 and 0487, and the hybrids in both 

 cases were brown ; and, when the hybrids were bred 

 from, their progeny were " blacks " and whites in the 

 ratio 3:1. The actual figures and ratios are : 



Parents Hybeids Hybrids' Progeny Ratio 



0358 X 0401 brown 86 " black " 33 white 2-6 : 1 

 0353 X 0487 „ 104 „ 46 „ 2-3 : 1 



The same variety, No. 0353, was crossed with two 

 other " black " varieties, and the result brought other 

 factors definitely into view. The colours of the hybrids 

 are not given, but the following table gives the colours 

 of the parents and the hybrids' progeny : 



