No. 597] EXPERIMENTS WITH PETUNIA 



the basis upon which these generalizations rest ; while the 

 fact that mixed F 1 families have now been obtained in the 

 case of a new wild form as well as with one nyctagini- 

 flora individual raised from wild seed, though not prov- 

 ing that the second statement would invariably hold good 

 for singles of each of these two species, certainly in- 

 creases the probability that this may be found to be the 

 case. 



With respect to these more recent experiments I was 

 able in 1911 to obtain a larger series of counts than had 

 been possible heretofore. For the opportunity to carry 

 out the work on this larger scale I was much indebted to 

 Professor Bateson, who kindly had some 5,000 plants 

 grown for me at the John Innes Horticultural Institution. 

 The results may be summarized shortly as follows : 



Seven crossbred singles out of matings in which the 

 four strains mentioned above were variously combined, 

 were self-fertilized. Only singles were obtained, viz., 

 1,200, 123, 89, 73, 33, 32, and 12 in the different families. 

 Total 1,562 singles. 



Fifteen singles were tested by crossing and pollen from 

 8 doubles was used to fertilize them. The single parents 

 included 



One violacea plant (commercial material, new stock). 



Twelve F x plants the offspring of 4 singles (Countess 

 of Ellesmere) which had been crossed with pollen 

 from various doubles (hybrida gniut/ifh.tra). Among 

 these 12 were 4 of those which had yielded all-single 

 families when self-fertilized. 



One hybrida grandiflora plant derived from a mating 

 between two singles each of which was the offspring 

 of a single crossed with pollen from a double. 



One F 2 plant derived from an F, single out of the mating 

 nyctaginifloraX hybrida grandiflora (double), the 

 F i plant having been crossed back with another 

 double. 



Thus doubleness was known to have been introduced 

 into the pedigree only once in the case of the first-men- 

 tioned (violacea) seed-parent, thrice in the case of the 



