Chapin: Heredity in Chimeras 



541 



spots are so few and small; while on 

 others dark green spots are large and 

 numerous. They have about 40% of 

 chlorophyll as compared with 30% in 

 "chlorina" plants. 



Here and there on "variegata" plants 

 one finds green branches which remain 

 green without producing variegated 

 leaves. vSuch branches are more com- 

 mon on heavily spotted plants, but they 

 may occur on any though some may not 

 happen to produce them. Branches 

 with pure "chlorina" colored leaves 

 might be expected, but they are not 

 mentioned and apparently do not occur. 

 "Variegata" plants are not true to seed. 

 The variegated branches produce 



1. "Variegata" plants between 90 

 and 100%,. 



2. Green heterozygotes, a few, whose 

 offspring are green and "variegata" 

 plants in the ratio of 3 : 1. 



3. Green homozygotes, a few, with 

 only green offspring. The green 

 branches on "variegata" plants behave 

 as heterozygotes producing green and 

 "variegata" seedlings in the ratio of 

 3:1. "Variegata" is recessive to green 

 and dominant to "chlorina," the F2 



generation segregating in each case in 

 the usual 3 : 1 ratio. Correns gives the 

 following Mendelian interpretation: 



Green (G) is dominant over "varie- 

 gata" (V) and both are dominant over 

 "chlorina" (C). The genetic character 

 of the germ cells in these plants would 

 then be : 



Green, GVC, GVc, GvC or Gve. 



"Variegata" gVC or gVc. 



"Chlorina," gvC. 

 He reports the results of a few crosses 

 between green plants whose germ cells 

 had the constitution (GvC) and "varie- 

 gata" (gVC). The F, plants were all 

 green (GgVvCC). The F. plants had 

 germ cells GVC, GvC, gVC and gvC in 

 equal numbers, which gave green, 

 "variegata" and "chlorina" seedlings in 

 the ratio 12 : 3 : 1. A Punnett square 

 may make this clearer to those who are 

 unfamiliar with Mendelian ratios. In 

 this square the male germ cells are 

 placed above the diagram and the 

 female cells along the left side. The 

 nature of the plant formed by the union 

 of any two cells is shown in the small 

 square where the columns intersect. 



Males 



In this experiment Correns obtained 

 106 green plants in the Fi generation. 

 Ten of these, self fertilized, gave in the 

 F2 generation 360 green, 76 "variegata" 

 and 28 "chlorina" plants, which agrees 

 well with the theoretical expectation of 

 348 green, 87 "variegata" and 29 

 "chlorina." 



The formation of green branches and 

 the fact that the variegated branches 



arc not true to seed is the difficult thing 

 to understand about these plants. Cor- 

 rens suggests that they are really in a 

 continual state of change from the 

 homozygotic, "variegata" condition to 

 the heterozygotic, green condition, but 

 this hardly explains anything. It is 

 simply stating the facts in another way. 

 And it may be questioned whether a 

 "variegata" plant which is constanth^ 



