ASTYLIS AND ORBICULARIS PHLOX 



Frontispiece. As an illustration of how genetics enables us to analyze the hereditary 

 make-up of living things this study of inheritance in phlox is instructive. The small, 

 white-flowered, astylis form was found in a supposedly pure strain of small-eyed phlox 

 (Figure i), and also appeared on inbreeding the large-eyed orbicularis variety. Crosses 

 were then made between astylis and small-eye and the plants of this first hybrid genera- 

 tion were all of the orbicularis type. That is, small-eyed and astylis are genetically pure 

 strains, which normally would be expected to breed true (if astylis were not self-sterile), 

 while orbicularis is of hybrid origin, containing the genes astylis and small-eye in the 

 heterozygous condition. The hereditary determiner of the small-eyed character is only 

 partially dominant over astylis, and the astylis "blood" has the effect of inhibiting the 

 development of anthncyan color except in the periphery of the petals. 



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