Chapix: Heredity ix Chimeras 



543 



VARIEGATED GERANIUM LEAVES 



The group at the left is from a seedHng whose father was a pericUnal chimera with white edged 

 leaves and whose mother was a green-leaved plant. The three leaves in the center are 

 from three different periclinal chimeras. The two leaves at the right show a reversal 

 of the usual condition in periclinal chimeras of the geranium. Here the green tissue is 

 on the outside and the white inside. (Fig. 15.) 



the F2 seedlings would then be green, 

 "variegata" and "chlorina" in the ratio 

 12 : 3 : 1 instead of the actual ratio of 3 

 green to 1 "variegata." To account 

 for this Baur assumes that factor coup- 

 ling occurs so that instead of all four 

 types of germ cells being formed, the Fi 

 plants produce only two having the 

 formulas Ab and aB. Just why Baur 

 did not make use of Correns' factors G, 

 V, and C which would seem to answer 

 the purpose equally well \vithout the 

 assumption of factor coupling is not 

 exactly clear. 



non-mendelian types. 



Instances of heredity which are to be 

 explained without the use of Mendelian 

 formulas are so rare that the following 

 types of inheritance possess an unusual 

 interest. 



The "albomaculata" type has been 

 described by Correns (11) for Four 

 O'Clocks, and by Baur (7) for Snap- 

 dragons. The plants have variegated 

 leaves irregularly spotted green and 

 white. Some leaves are nearly white 

 with the green spots few and small 

 while others are nearly green with little 

 white. All graduations of color exist 

 between these. There are also branches 



with pure white or pure green leaves 

 which do not become variegated after- 

 wards. Anatomically it is seen that the 

 chloroplasts are bleached out more or 

 less in the white areas and the change 

 from green to white spots is a gradual 

 one. Chloroplasts may even be un- 

 equally bleached in the same cell. 



The green branches produce green 

 offspring which are true to seed. White 

 branches yield only white seedlings 

 which soon die. Variegated branches 

 produce, in addition to these, "albo- 

 maculata" plants which live or die 

 according to whether they have or have 

 not sufficient chlorophyll to sustain life. 

 The ratio of green, white and variegated 

 offspring from variegated branches is 

 different in diflFerent plants, but still it 

 seems to bear a direct relation to the 

 amount of green and white in the leaves. 



The pollen from "albomaculata" 

 plants behaves in crosses as if it came 

 from normal green ones. For instance 

 the pollen from a blossom on a white 

 branch of an "albomaculata" plant was 

 used on castrated flowers of a "chlorina" 

 plant. The Fi plants were all green 

 with green and "chlorina" seedlings in 

 the ratio of 3 : 1. No "albomaculata" 

 plants appeared. Likewise no segrega- 



