VARIATION IN PEDIGEEE-CULTUEES 



22 1 



discontinuous variations or mutations are essentially vegetative, vet 

 these are generally termed so exclusively. It is to be noted that such 

 sports, or mutants, when closely fertilized, come true to their aberrant 

 characters. Among other numerous conclusions sustaining this point, 

 one which has recently come to notice again is that of Kerner, 3 who 

 said : 



The fact is that all plants may at some time sooner or later produce an 

 aberrant branch, which differs from the parental type in many characters, and 

 numerous phenomena force us to the conclusion that under the conjunction of 

 favorable circumstances such aberrants would become the starting points of new 

 species. 



In the context the author is careful to point out the limitations of 

 such a method of origin of forms. 



Fig. 7. (Kaothera biennis, the Common Evening Primrose. 



Actual pedigrees from such sports or aberrant branches have been 

 tested, in one instance by de Tries and in two others by myself, with the 

 unanimous result that they were found to be constant to their aberrant 

 characters. 



Having carried on such pedigree-cultures with a large number of 

 species for several years and having encountered some which did and 

 others which did not give rise to aberrant individuals, attention was 

 directed to the possibility of inducing changes in the hereditary ele- 

 ments in such a manner that the qualities transmitted would be altered 

 or destroyed. A theoretical consideration of the subject seemed to 

 indicate that the changes constituting the essential operation of muta- 

 tion ensued in a stage previous to the reduction divisions in the embryo- 

 sac, or the pollen mother cells. It was planned therefore to subject 



3 ' Die Abhiingigkeit der Pflanzengestalt von Klima und Boden, 



Innsbruck, 



?S09. 



