F. C. Miles 199 



self-polliuated, yielded a progeny about one-fourth of which was non- 

 green. 



TABLE I. 



The result of self-pollinating and also of crossing tivo types of 

 heterozygous green platits. 



Striped 



— 10 — ) 



- - lel 97 - 



As a working hypothesis it was assumed that the presence of two 

 factors is responsible for the processes which finally result in normal 

 green colour. For convenience, these factors will be designated by "A" 

 and " B," respectively. Then in the category in which pure white plants 

 occur let a heterozygous green individual be represented by the zygotic 

 formula AABh. When a plant of this nature forms its germ cells they 

 would be of two kinds, viz., AB and Ah. Upon self-pollination the next 

 generation would consist, on an average, of plants in the following ratio : 

 one green plant having the formula A ABB, and which in later genera- 

 tions would breed true green ; two gi-een plants having the formula 

 AABb, which in the next generation would segregate into three gi-een 

 plants to one white one ; and one white plant having the formula AAhh, 

 the white jjlant soon dying. Here, in the absence of the factor " B," 

 the plant is pure white, the factor "A" being unable to bring about 

 the formation of any colouring material whatever. 



In the category in which yellowish-white plants occur let the zygotic 

 formula AaBB represent a heterozygous green plant. If this plant be 

 self-pollinated, the next generation would consist of approximately three 

 green plants to one of the yellowish-white type. One-third of the green 

 plants would have the formula AABB and consequently would breed 

 true, while two-thirds of the green individuals would have the formula 

 AaBB and in the next generation would segregate in the regular 

 manner. The yellowish-white plant would be represented by aaBB. 



' The striped individual had only a faint white stripe in one of its leaves. Otherwise 

 it was fully green. 



