1922] 



Setchell-Goodspeed-Clausen : Nicotiana Tahacum 



507 



tions of the same series, viz., I6F2H03P5 ; I6F2H23P30 ; I6F2H03P34 ; 

 I6F0H04P28 ; and I6F2H24P33. The segregation in the resulting popu- 

 lations is recorded in table 19. 



The method of studying these flowers was the more accurate one 

 previously described in connection with later generations of the 

 (Uigustifolia-macrophyUa series. In the classification of flowers it was 

 noted that reds and whites were sharply distinguishable from pinks. 

 The pinks were of many different shades ; some very light, others rela- 

 tively dark, corresponding to the range obtained in the angustifoUa- 

 macrophylla series. However, in these populations the range of vari- 



TABLE 19 



F2 SEGREGATION IN 1916 SOWINGS OF ALBA-MACROPHYLLA SERIES. 



ation of pink appeared to be greater and the intergradations more 

 gradual than in that series. In the whites there was also evidence of 

 differentiation into classes depending upon the amount of yellow or 

 creaminess in the flowers. Some of the whites appeared to belong to 

 a clear white albino class, but most of them had a distinctly creamy 

 tinge. The observed segregation in these populations was in almost 

 exact agreement with the formulation advanced above. 



4. F3 AND SUBSEQUENT GENERATIONS OF THE ALBA-MACROPHYLLA 



SERIES 



In table 20 we have summarized the behavior of the F3 populations 

 as respects color of flowers and height of plant. Of the five red F2 

 plants from which F3 populations were grown, three proved to be 

 homozygous for red and one proved to be a heterozygote of the genetic 

 constitution rrWw. Of this latter selection two sowings were made, 

 one in 1912 and another in 1913. The combined results from these 

 two sowings, .35 red: 14 white, are in fair agreement with Mendelian 



