564 



DOUBLED CHROMOSOMES OF OENOTHERA 



than one chromosome, and it is usually assumed that factors of the 

 other doubled ones are influencing the visible features of the plants. 

 Even if only one chromosome is doubled, however, our plants may 

 show deviations from their prototype, and in such cases we must 

 suppose that in the same rod different groups of factors have become 

 mutated. 



Pure types have occurred in our experiment only in specimens 

 having one rod doubled, as will be seen in table V. In this table 



only the flowering plants are mentioned, but it is to be remarked 

 that for spathulata 6 specimens which did not produce flowers could 

 be added to the last column. The specimens of oblonga, auricula, 

 candicans and hamata were sufficiently pure to their types, and of 

 the pulla, for which no prototype is as yet known, all had the same 

 form, with only one exception (with 16 chromosomes). It must be 

 remarked, however, that numerical relations of this kind are very 

 changeable among the progeny of semigigas, and that other crosses 

 of it have given different results. It is, therefore, only on the main 

 points that we wish to lay stress. Numerous types may lay hidden 

 in the germs of the non-germinating seeds. 



Characters of mutants 



The different forms of mutants seen in our cultures will be descri- 

 bed, beginning with the largest group, the cana-like, plants. It is 

 at the same time the most complete, and the incompleteness of the 

 other groups may therefore be ascribed to their smallness. 



Prototype cana. — Seven plants were exactly like the race of this 

 name, which has been described by one of the writers (5), and of 



