2l8 R. RUGGLES GATES. 



meiotic divisions, for transforming the original 3:1 ratio into a 

 15:1 by merely redistributing the chromosome pairs. 



In concluding this paper it is desirable to compare the related 

 but different results recently obtained by Honing,^ with two 

 varieties of Canna indica which are naturalized in Sumatra. 

 One variety has green leaves while in the other the leaves have a 

 broad red margin. 



From the offspring of plants of the latter variety Honing 

 obtained ratios red : green of 3 :i , 9 7 and 27 :$7. The same ratios 

 were obtained in crossing the two varieties. These ratios are 

 accounted for by the hypothesis that the cooperation of three 

 "factors" is necessary to produce the red margin. If these are 

 located in chromosomes belonging to three different pairs, 

 then the resulting ratio should be 27 red: 37 green, since the 

 character can only appear in the presence of all three factors 

 A, B, C. On the other hand, if all three factors are located in 

 the same chromosome a 3:1 ratio would be obtained, while if 

 two of them were in one chromosome and the third in a chromo- 

 some of a second pair, the ratio would be 9:7. 



It was found that in certain cases plants in families having a 

 3 :i ratio gave rise in the next generation to a 9 :7 or 27 137 family. 

 In such cases one may assume that a mutation has taken place 

 resulting in a redistribution of the determiners, the three which 

 were present in one chromosome being rearranged so that they 

 are in chromosomes belonging to two or three different pairs. 

 So far as I am aware, this is the first experimental evidence that 

 an actual rearrangement of the chromomeres in the chromo- 

 somes is one of the kinds of change which the nucleus may 

 undergo, the case being somewhat different from Morgan's 

 well-known phenomena of "crossing, over" in Drosophila. 

 Further experiments are necessary to test the nature of this 

 evidence for the occurrence of mutations in which such a re- 

 arrangement of the nuclear material can take place. 



Summary. 

 Nilsson-Ehle was the first to show that duplicate and triplicate 

 factors for red are present in certain strains of wheat. He 



1 Honing, J. A., 1915, " Kreuzungsversuche mit Canna- Varietaten," Rec. Trav. 

 hot. NHrlandais, Vol. 12: Livr. 1, pp. 26. 



