5r.fi 



THE AMERICAN NATURALIST 



[Vol. XLIX 



Another F 3 family (No. 149) was derived from an F 2 

 plant (65. III. 12) having sepals weak red with the color 

 pattern as extensive as in rubrinervis 6 (*. e., nearly the 

 extreme condition), and in addition streaks of pale red 

 on the hypanthium. This plant was therefore nearer r 

 than R, and one may account for its occurrence through 

 " contamination" before segregation took place in the 

 germ cells of the previous generation. In pure rubri- 

 nervis or grandiflora I have never found even a trace of 

 red on the hypanthium until the flower fades. The off- 

 spring of this plant numbered 186 individuals and their 

 pigmentation fluctuated about that of the parent plant as 

 a mean. This condition closely approximated that in (E. 

 rubrinervoides (1915c, p. 390), which may have orig- 

 inated in a similar way. 



We must, therefore, conclude that plants which are 

 intermediate in pigmentation breed true, at least in all 

 cases tested, and that the degree of pigmentation in the 

 parent is adhered to in the offspring whether the parent 

 plant is an under-pigmented R or an over-pigmented r. 

 In this aspect, the inheritance in such cases is quantita- 

 tive and the offspring vary only within narrow limits. 



The quantitative aspect is further emphasized when F x 

 and F 2 hybrids of (E. grandiflora and CE. rubricalyx are 

 crossed back with either parent. The pigmentation is 

 much intensified when crossed back with rubricalyx, and 

 greatly diluted when crossed with grandiflora. Thus in 

 (rubricalyx X grandiflora) X grandiflora if the female 

 parent is heterozygous for R, segregation into R and r 

 plants will occur in the offspring, but the R plants will 

 be much paler than in the selfed offspring of the female 

 parent. 



Hence there are two somewhat antagonistic effects 

 which have to be considered, (1) the segregation of R and 

 r individuals, and (2) a permanent dilution of the pig- 

 mentation of the R individuals. The former effect can be 

 explained by the meiotic mechanism which segregates 



