19--] Setchell-Goodspeed-Clausen: Nicotiana Tahacum 519 



Obviously this formulation would account for AUard's results with- 

 out contradicting those which we have presented, but inasmuch as our 

 experimental evidence is not yet complete we refrain from any further 

 discussion of the consequences of this scheme save one. Allard presents 

 certain data for a cross of carmine x white which gave in F^ light 

 carmine, and in F, 3 colored : 1 white, the colored being various shades 

 of carmine and pink. Allard 's discussion of this case is somewhat 

 mixed, but he evidently erroneously expected a simple monohybrid 

 segregation of the 1:2:1 kind. That more than one factor is con- 

 cerned in the cross is clearly shown by the results of crossing some of 

 the extracted whites with pink varieties. The results of three such 

 crosses gave : 



1. Pink (Maryland Mammoth) x Extracted white 36 carmine : 18 pink 



2. Extracted white x Pink (Maryland Mammoth) 20 carmine : 23 pink 



3. Pink (Conn. Broadleaf) x Extracted white 12 carmine : 39 pink 



Totals 68 carmine : 70 pink 



In (1) above we have combined in the carmine class 17 carmine and 

 19 somewhat lighter than carm;ine. 



If we consider a cross of dark red x white according to the genetic 

 formulation given above, the F^ should be dark red, and Fg should 

 consist of 9 dark red : 3 pink : 4 M^hite. Doubtless the pinks and the 

 dark reds would exhibit various shades, but the three classes should 

 be distinct. If we combine "carmine" and "lighter than carmine" 

 to form a carmine class and dark and light pink to form a pink class, 

 Allard 's F, data reduce to the following form : 



149 carmine : 64 pink : 65 white. 

 This ratio compares very favorably with a 9 : 3 : 4 expectation, viz. : 



157 dark red : 52 pink : 69 white. 

 No F3 results from sowings from colored F, plants are given, but the 

 single F2 white, which gave when crossed with pink approximately 

 equal numbers of carmine and pink flowering plants, is accountable 

 for as of the genotype wwRRPp. Further investigations are in pro- 

 gress for the purpose of determining precisely the relation of dark 

 red and pinkish to the red, light pink, and white colors reported upon 

 in this paper. 



There are other references in the literature to Mendelian inherit- 

 ance in Tahacum., but inasmuch as these do not bear upon the 

 characters which we have attempted to analyze it does not appear 

 necessary to discuss them at this point. 



