4| S Lutz, Triploid Mutants in Oenotiiera. 



first, was recognized in a seventh culture. The chromosome number 

 of this plant was not determined, but was found to be not less 

 than 20 nor more than 22. 



A third mutant, also represented by a single individual, having 

 vegetative characters quite distinct from those of the two preceed- 

 ing, and having 22 chromosomes, was found in an eighth culture 29 ). 



All of the above 10 individuals were of known parentage and 

 descended through guarded fertilizations from seeds or plants from 

 de Vries. 



From the foregoing it appears that the evidence is not lacking 

 to demonstrate the occasional occurrence of triploid mutants in 

 Oenotliem. We may now consider the evidence at hand in regard 

 to the relative frequency of triploid and tetraploid mutants. 



Davis, in a recent publication (4), has called attention to a most 

 important point in the following statement : 



"Thus yiyus at the most has been noted only seven times, and, 

 since apparently the cytology of de Vries 1 strain alone has been 

 studied, it is by no means certain that all of the forms reported 

 later are the same as the first example from de Vries' cultures 

 of 1895." 



In my studies of the Oenotheras (as repeatedly stated heretofore) 

 I have found no exception to the rule that all plants having the same 

 vegetative characters from the seedling stage to the end of the flowering- 

 period, -- have identical chromosome numbers. Therefore, each mutant 

 that was certainly proven to have had the same vegetative characters 

 as de Vries' 1895 0. yiycts mutant, probably had the same chromo- 

 some number as the latter form. So many difficulties attend the 

 certain identification of mutant 0. yiyct* that I doubt if any one 

 but Professor de Vries is capable of identifying it with certainty, 

 for he alone has the mental picture of the original plant. Those 

 of us who have gained our impressions of the vegetative characters 

 of this form chiefly from the study of the inbred descendants may 

 not be able to judge correctly. Furthermore, we can not rely upon 

 the number of chromosomes for the identification of 0. yiycts, any 

 more than we can assume that 14 chromosomes proves a plant to 

 be 0. Lamarckiana. 



Although all of 7 individuals in question were observed by 

 de Vries (de Vries M, MacDougal 1, Schouten 3), the iden- 

 tifications were made before it was known that other forms possessed 



29) Another plant was observed in a ninth culture (0. Lamarckiana X 0. 

 Lamarckiana) in 1908 which has not been included in this report as the card bearing 

 the description of its vegetative characters was lost. However, it is marked on the 

 I'.lnS chart as "(/if/as-\\ke\ and, as I have two fixations of root-tips from this plant 

 I hope to be able to determine its somatic chromosome number at least approximately. 

 I! i> probable that it also was a triploid mutant. 



