530 



THE AMEBIC AN NATURALIST 



[Vol. XLVII 



to be alternative. It is on this hypothesis that I shall 

 treat the red coloration of papillae as a dominant char- 

 acter when for convenience employing* a Mendelian nota- 

 tion in the accounts that follow. 



It became a matter of interest to determine how repre- 

 sentatives of Class I and Class II would behave in the F 2 

 when selfed and how they would behave when crossed 

 reciprocally. Therefore I selected a plant, 11.35m 

 (Davis, '12a, Figs. 6 and 7), as representative of Class I, 

 and a plant, 11.35a (Davis, '12a, Figs. 5, 8 and 9), as 

 representative of Class II, and according to my plan 

 (Davis, '12a, p. 399) carried these in pure lines into an F 2 

 and also grew the crosses 11.35 m X a and 11.35 a X m. 

 Furthermore, a large F 2 generation was grown from an 

 especially interesting plant 11.35La (Davis, '12a, Figs. 

 10, 11, 12 and 13), also representative of Class II, which 

 resembled (Enothera Lamarchiana closely in certain par- 

 ticulars. These cultures will now be briefly described. 



1. The F 2 Generation from 11.35m.— From this plant, 

 with red papillae on green portions of the stem as in the 

 parent biennis, the contents of one capsule, 413 seeds, 

 were sown. The culture, 12.43, produced 180 seedlings, 

 of which 166 plants were brought to maturity. Among 

 these, 86 plants presented the stem coloration of 11.35m 

 and the biennis parent of the cross, and 80 plants pre- 

 sented the stem coloration of the ynuuliflora parent. 



Let us assume the formula for the biennis parent to be 

 Rr {R standing for the presence of the factor responsible 

 for the red color of the glands and r for its absence) ; i. <?., 

 the bieymis parent is held to be heterozygous for this 

 character and to form two classes of gametes, viz., R and 

 r. Let us assume that the formula for the grandifora 

 parent with respect to this character is rr. The F 4 

 hybrid plant 11.35m would then be expected to have the 

 formula Rr and to produce gametes R and r. These 

 gametes in chance combinations should give F 2 hybrids in 

 the proportions 1RR : 2Rr : lrr, which would be a 3 : 1 ratio 

 with respect to the appearance of the character R (red 



