1922] Setchell-Goodspeed-Clausen: Nicotmna Tahacum 509 



for pink in F,. This, however, is not inexplicable, for only one in 

 nine among the F, pinks should belong to the RRWW genotype. 



Sowings were made from seven white F^ plants. Among 190 plants 

 so produced there was one pink flowering individual. It surely rep- 

 resents some kind of experimental error. We may say, therefore, that 

 for flower color the formulation advanced to account for the Fo segre- 

 gation ratio, also accounts for the behavior observed in the various F3 

 populations. 



We have reported the data on height in table 20, largely in order 

 to show that this character, although obviously dependent on factor 

 differences, is so complex as not to permit of a simple qualitative 

 treatment. Thirteen F,, sowings from tall F^ plants gave ten popu- 

 lations showing only tall plants. Two of the remaining populations 

 showed segregation into 31 tall (and medium) : 13 short. One popu- 

 lation consisted entirely of short plants. The classification of the Fg 

 parent of this plant as "tall" was noted as doubtful at the time, the 

 note ''or medium" being appended. Two populations were grown 

 from Fo plants of medium height. One of these populations was uni- 

 formly of low stature; the other showed segregation into 19 tall (and 

 medium) : 4 short. Six populations were grown from F^ parents, 

 four of which apparently bred true for low stature, the other two 

 showed segregation into tall (and medium) or short in the ratio 42 : 8. 

 It is interesting to note that at the time of classification the parents 

 of these two later populations were classified as short (or medium), 

 indicating a doubt as to proper classification. More definite data will 

 be necessary before a satisfactory formulation of these height differ- 

 ences can be made, but certain of our results seem to indicate that 

 there is one allelomorphic pair which has a rather marked effect on 

 stature, and that there are other subsidiary pairs of factors which 

 have less marked effects. 



Only one line in this alba-macrophylla series was carried out to 

 subsequent generations to demonstrate the possibility of fixing char- 

 acter complexes from a hybrid. It was a low stature white flowering 

 line. In F4, 100 plants of 13F,Ho4P34P23P2 bred true to low stature 

 and white flower color. The population was uniform, the plants ex- 

 hibited the general habit of macrophylla rather than that of alba; and 

 the leaves were the same shape as those of macrophylla, but they were 

 slightly rugose, although not so much so as those of alha. In F,.„ two 

 populations of 25 plants each were grown, viz., 14F-H24P34P2.!P2P4t 

 and 14F-H.4P34P2..,P.2P83. No differences were detectable between these 

 two populations, and the characters exhibited were those we have noted 



