342 



The Journal of Heredity 



PLANTS OF THE THREE TYPES 



Figure 4. The effect of the astylis gene seems to be to inhibit the development of 

 anthocyan color in the central "eye" of the flower, when in the heterozygous condition, 

 and to result in the development only of this "eye" region of the petals when it is 

 in the "pure" or homozygous state. Note that the size of the astylis flower is approxi- 

 mately that of the "eve" region in the flrbicularis form. 



ment of the anthocyan color in the 

 corolla to a narrower peripheral ring, 

 curiously enough, the large white eye 

 is not brought out when the astylis gene 

 is homozygous. It seems then to cause 

 the cutting off from development of the 

 corolla periphery, the part that would 

 show the blade color, leaving merely the 

 large white eye; hence, too, the small 

 size of the flower blade. A white astyl- 

 is bloom may be looked upon as just the 

 eye region of a flower with large white 

 eye that has lost its periphery due to 

 the absence of the gene. Figure 3 

 represents one entire family secured by 

 inbreeding an orbicularis parent whose 

 large white eye was surrounded by a 

 Tyrian-pink border. All the non-astylis 

 plants have borders of this color, but 

 the astylis sibs of these colored plants 

 are white or practically so. Occasionally 

 a faint fleck or tinge of anthocyan 

 may be detected on such plants. 



Is it jxjssible to interpret this situa- 

 tion on the basis of a close linkage of 



factors for white and astylis f Certain 

 details of the experiments make this 

 proposition unlikely. Some of the or- 

 bicularis plants of 1 921 were heterozy- 

 gotes of white and cream." The cream 

 had been introduced through a normal 

 non-a.s'^y//s parent. In 1922 six such 

 heterozygous orbicularis plants gave 218 

 progeny as shown in the accompanying 

 table. 



These data indicate no linkage of 

 white and astylis. 



The large-eyed condition found in 

 the variety orbicularis, therefore, is a 

 heterozygous character and presents a 

 genetic situation similar to that already 

 reported by the author for the fimbriate 

 phlox." (Jne could not expect to se- 

 cure a true-breeding strain of orbicu- 

 laris with the existant genetic constitu- 

 tion of Phlox drmnmondii, but this in- 

 vestigation shows that stands which 

 are one hundred per cent orbicularis 

 may be obtained by hybridizing astylis 

 and the small-eved varietv. 



Table i. Distribution of the Pror/rny of Six Orbicularis Plants. 



Astylis 



White Cream 



40 10 



Orbicularis 



White Cream 



80 24 



Small-eyed 



White Cream 



49 15 



^The writer has already shown that cream is a simple recessive of white. See Genetics, 

 V; 189-248. 



