Gates: On the Nature of Mutations 



105 



A DIFFERENT TYPE OF MUTANT 



Oenothera rubricalyx originated in the breeding-plot of Dr. Gates in 1907 and is quite unlike 

 all the other primrose mutants. It did not spring directly from Lamarck's primrose, but 

 from a mutant of it, Oe. rubrinervis. In the mutant here shown the under sides of the 

 leaves, and the flower stalks, are red, whereas in the parent they are green. Dr. Gates 

 assumes that some chromosome in the reproductive cells has undergone a chemical change, 

 which leads to an increased production of red pigment, and thus to the mutation. (Fig. 6.) 



Another interesting fact concerning 

 gigas is that its inheritance is entireh' 

 different from that of lata, since gigas 

 breeds true except for remarkable varia- 

 tion chiefly in foliage. This variabil- 

 ity is probably concerned with new 

 combinations of the double chromosome 

 series. In crosses also gigas behaves 

 differentlv from lata, giving intermediate 



hybrids which essentially breed true. 

 This difference in behavior of gigas and 

 lata is undoubtedly concerned with the 

 different chromosome content of the 

 two forms, and is explainable in terms 

 of those differences. 



If now we consider rubricalyx, we find 

 the type of change entirely diverse 

 from either of those mentioned above. 



