Heredity Studies in the Morning-Glory 15 



It is possible that some of the genetically tinged whites were classed as 

 true whites. 



In pedigree 200, arising from a cross between a light blue and a magenta, 

 the Fi plants were light purple. Plants grouped in this type vary greatly 

 in color and are usually heterozygous for several factors. If when selfing 

 a light purple plant the genes B and I were lost in the recombinations, 

 then pinks and mauves would result. If R also were simplex in such a 

 light purple Fi plant, there would be a possibility that pinks and tinged 

 whites might appear. Such seems to have been the case in this pedigree, 

 where the second-generation plant 200-2-6, a tinged white, was selfed 

 and gave a progeny consisting of 6 mauves, 2 pinks, 10 tinged whites, 

 and 6 whites. The Fi parent plant probably carried the genes X, B, and I 

 in simplex condition, and they became lost out of the recombination 

 that gave rise to plant 200-2-6. If this plant had been of the constitu- 

 tion CCRrXx, its behavior as described above could be explained, for 

 then it could have given, when selfed, 



CCRRXX mauve 



CCRRXx mauve 



CCRRxx pink 



CCRrXX tinged white 



CCRrXx tinged white 



CCRrxx tinged white 



CCrrXX white 



CCrrXx white 



CCrrxx white 



All the phenotypes here given were actually represented in the Fo progeny 

 of this individual. 



The genetic behavior of tinged whites may be explained on the 

 hypothesis of a formula CCRr. When selfed, then, they should throw 

 pinks, tinged whites, and whites. Such was here found to be the case, in 

 general, when the tinged whites were selfed, with the exceptions of the 

 cases discussed above. 



Type 3 Pink (Plate I) 



Description of the type. — The type called pink is a very pale rose and 

 somewhat lighter than the type here called mauve. It may be either paler 

 or slightly more intense, factors such as water supply, vigor of the plant, 

 amount of light, and so on, seeming to affect its intensity. It is paler 

 and less blue than mauve, type 4. 



Theoretical consideration of data. — If the chemical theor\^ of color pro- 

 duction as explained on page 9 is adopted, the pink type must be con- 

 sidered as the lowest in the series of color varieties of the morning-glory, 

 hypostatic to all the others, and due to the addition to the white geno- 



131 



