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THE AMEBIC AN NATURALIST [Vol. XL VIII 



Linkage Cases in Primula 



In the case of primula, linkage was first found between 

 red (versus green) stigma and red (versus magenta) 

 flower color. Long style (versus short) and dark stem 

 (versus light) were found to he linked with red stigma. 

 Indications were observed that still a fifth gene, a domi- 

 nant which reduces the color of the flower to a tinge in the 

 corolla tube, belonged to this group. 



A hack cross involving the three genes, red stigma, red 

 flower and long style was made. Credit is due to Gregory 

 for the use of this method for obtaining linkage data. 

 Unfortunately many of the individuals were useless for 

 the linkage of red flower color, because of the occurrence 

 of white ; and the numbers are small. 



In Table V, I have summarized the data given by 

 Gregory. 4 



TABLE V 

 The First Chromosome of Primula 

 Red Stigma and Red Flower 



Coupling F 2 1,174 305 289 232 .511 1.8:1 35.3 



Red Flower and Long Style 



Coupling back cross. 40 53 6 5 8.4:1 10.9 



Bed Stigma and Long. Style 



Red Lon™* Ty£ Stfgma Long 



Cnupliny Lack cross. 44 64 35 30 1.6:1 37. 



*Jour. Genetics, '11, Vol. I; Proc. Boy. Soc, '11, Vol. — 84. 



