166 GENETICS IN RELATION TO AGRICULTURE 
the basis of independent segregation of the factors indicates a fairly 
close correspondence between the two. It may be of some significance, 
however, that walnut and rose are the deficient classes in both cases. 
From the standpoint of factor interaction this case is of interest 
because it shows clearly that the character expression of a given set of 
factors cannot be predicted with certainty from the known character 
expression of some of these factors. It would have been impossible 
to predict from the character expressions involved that rose X pea 
would give walnut-comb fowls or that by recombination of the two 
recessive factors involved a single-comb fowl would result, for these 
two new comb types are totally different from the rose and pea types 
from which they can be derived. The obtaining of new characters of 
this kind by factor recombination is by no means an unusual thing in 
genetic experiments, and is sufficient justification in breeding work for 
testing factor combinations to determine what sort of character ex- 
pression may result from them. 
CRVH CrVH cRVH crVH 
CRVH | CCRRVVHH CCRrVVHH CcRRVVHH CcRrVVHH 
Violet hairy Violet hairy Violet hairy Violet hairy 
CrVH| CCRrVVHH CCrrVVHH CcRrVVHH CcrrVVHH 
Violet hairy | Cream glabrous Violet hairy Cream glabrous 
cRVH| CcRRVVHH CcRkrVVHH ccRRVVHH ccRrVVHH 
Violet hairy Violet hairy White glabrous | White glabrous 
crVH | CcRrVVHH CerrVVHH cckrVVHH corr VVHH 
Violet hairy | Cream glabrous | White glabrous | White glabrous 
| | 
Fia. 77.—F2 checkerboard analysis of a cross between two varieties of stocks, white 
glabrous (ccRRVVHH) and cream glabrous (CCrrVV HH). 
Miss Saunders’ Factor System in Stocks.—A more complicated case 
of factor interaction as related to character expression has been in- 
vestigated by Miss Saunders in stocks (Matthiola) and has been inter- 
preted in somewhat the following fashion with respect to the factors 
and factor relations therein concerned. 
C—a factor for chromogen base which by itself gives a cream-colored 
flower. Its allelomorph, c, gives white flowers. 
R—a factor for red coloration, epistatic to C. 
V—a factor for violet coloration epistatic to R. 
H—a factor for the production of hairs on the leaves, active only in the 
presence of C and R. 
The complicated relations existing between these factors are well 
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