De Vries: Atavistic Variation in Oenothera 



81 



root leaves. In my cultures these side-stems do not ordinarily 

 become tall enough to bear flowers. But by cutting out the main 

 stem at an early period I could induce the others to a more vigor- 

 ous growth. I repeatedly made this experiment ; but will only 

 cite here observations made on a single plant in the summer of 

 1 90 1, grown from seed of a purely cruciate parent. It made six 

 side-stems, out of which three bore only atavistic or broad-petalled 

 flowers. The three other stems likewise produced obcordate 

 petals, but not exclusively, bearing on one side of the spike flowers 

 with the narrow and variable petals of the above-named intermedi- 

 ate types. 



Such cases prove that the atavistic individuals are not, or at 

 least are not always, so constant as could be deduced from the 

 figures above given. Analogous instances of sectorial variation, 

 one sector of the spike bearing other flowers than the remaining 

 sectors, were from time to time observed on atavistic individuals 

 and also on intermediate ones, the sport giving flowers with ob- 

 cordate petals. As yet I have found no such sports on plants of 

 the purely cruciate type nor purely cruciate flowers on those of the 

 two other types. But I have no doubt that this is only due to the 

 small extent of my cultures. 



1901. 



f 4th generation. 



1 5th generation. 

 1900. 4th generation. 



1899. 3d generation. 



1898. 2d generation. 



1897. 1st generation. 



Pedigree of 



Oenothera cruciata varia 



Number of individuals of each type :' 

 Cruciate. Intermediate, Atavistic. 



44 22 



39 



24 



30 



30 



(No. 1.) (No. 2.) (No. 3.) 



45 



71 70 



58 



