TYPES OF FACTOR INTERACTIONS 167 
illustrated by the cross white glabrous (ccRRVVHH) X cream glabrous . 
(CCrrVVHH). This gives in F violet hairy plants (CeRrV VHH) which 
segregate in F, according to the analysis given in the accompanying 
checkerboard (Fig. 77). The proportions are 9 violet hairy:3 cream 
glabrous:4 white glabrous. 
The peculiar feature of these relations is the fact that the factor H 
for hairiness can only act in the presence of Cand R. In fact as far as 
the above experiment goes, the hairy condition might be considered as 
merely an extra effect of the interaction of C and R. However, glabrous 
violet plants are known and in these the factor h for the glabrous con- 
dition must be present. When a violet glabrous (CCRRVVhh) plant 
is crossed with white glabrous (ccRRVVHH) the F; again is violet hairy 
(CcRRVVHh), this time because the factor for hairiness is brought 
in by the white plant, and in F, the segregation is as indicated in the 
CRVH CRVh cRVH cRVh 
CRVH | CCRRVVHH CCRRVVHh CcRRVVHH CcRRVVHh 
Violet hairy Violet hairy Violet hairy Violet hairy 
CRVh| CCRRVVHhA CCRRVVhh CcRRVVHh CcRRVVhh 
Violet hairy Violet glabrous Violet hairy Violet glabrous 
cRVH| CcRRVVHH CcRRVVHh ccRRVVHH ccRRVVHh 
Violet hairy Violet hairy White glabrous | White glabrous 
cRVhA| CcoRRVVHh CcRRVVhh ccRRVVHh ccRRVVhh 
Violet hairy Violet glabrous | White glabrous | White glabrous 
Fic. 78.—F:2 checkerboard analysis of a cross between violet glabrous (CCRRVVhh) and 
white glabrous (ccRRVVH#H) stocks. 
checkerboard in Fig. 78. The phenotypic ratio obtained this time is 
9 violet hairy:3 violet glabrous: 4 white glabrous. 
This analysis not only adequately accounts for the phenomena as 
given above, but it also accounts for the F3 results and the various types 
of results that are obtained by mating other genotypes. In addition 
Miss Saunders found that when purple or white ¢zncana were mated to 
cream of the type above, the entire series of forms recorded for the 
previous white X cream mating were obtained and in addition cream 
hairy and cream glabrous. This at first sight appears to contradict 
the hypothesis that no cream or white hairy forms are possible. But 
closer examination has revealed the fact that white zncana, which is 
itself hairy is in reality a colored form, 7.e., possesses the factors C and 
R. This is shown by the fact that a slight tinge develops in flowers of 
this variety on fading, and in the F; from a cross of this form with cream 
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