NEW DIMORPHIC MUTANTS OF THE OENOTHERAS. 89 



Lamarckiana and 3 oblonga. Although these cultures do not justify 

 the calculation of percentage figures, they evidently support the 

 conclusions drawn from the three former ones, and argue for the 

 conception that this form of splitting is typical for 0. cana. 



Influence of culture on percentage figures. — I have shown 1 ) 

 that the percentage figures for the splitting of 0. scintillans in 

 the succeeding generations may differ for different families. Some- 

 times it is only 15 per cent, more often it varies between 34 and 

 39 per cent, and in rare cases it reaches 69-93 per cent. Subsequent 

 experiences have suggested the idea that these differences are 

 due mainly to outward conditions or to the method of cultivation, 

 and that favorable influences must increase the percentage of indi- 

 viduals with the type of scintillans and diminish the percentage of 

 Lamarckiana-tike specimens. 



The self-fertilized seeds of the cana individuals previously 

 mentioned have given the following percentages of specimens 

 with the cana type: 15 and 16 per cent, 24-34 and 35 per cent, and 

 46 and 60 per cent, the two latter being found in a culture which 

 excelled the others in vigor. Evidently these figures run parallel 

 to those of scintillans and the variability must have the same cause 

 in both cases. 



In order to ascertain the nature of this cause I have tried to 

 answer two questions, namely: (1) are the percentage figures 

 different on different parts of the main spike of a plant and on 

 different branches; and (2) are they different for annuals and 

 biennials, provided that the individual strength is in both cases as 

 great as possible? The following experiments will show that the 

 first question is to be answered in the negative, but the second in 

 the affirmative; or in other words, the percentage figures depend 

 upon individual vigor of the plants, and this between the widest 

 possible limits. 



The second generation of mutant no. 3, cultivated in 1913, was 

 the most vigorous of all my annual cultures, as already mentioned. 

 I chose for my experiment, therefore, the strongest individual of 

 this group, having the largest supply of pollen in its anthers, and 

 fertilized its flowers on the main spike and on a lateral branch in 

 small bags, each with its own pollen. At the time of harvest I 

 separated the fruits in groups of 10 each; there were 4 of these 

 groups on the main spike and 2 on the branch. In the spring of the 



i) The mutation theory, Chicago, 1909, pp. 388 — 391. 



