56 MENDELISM CHAP. 



of the corolla. In most primulas the eye is small, but 

 there are some in which it is large and extends as a flush 

 over a considerable part of the petals (Fig. 10). Experi- 

 ments showed that these two pairs of characters behave 

 in simple Mendelian fashion, short style (= "thrum") 

 being dominant to long style (= "pin") and small 

 eye dominant to large. Besides the normal long and 

 short styled forms, there occurs a third form, which has 

 been termed homostyle. In this form the anthers are 

 placed low down in the corolla tube as they are in the long- 

 styled form, but the style remains short instead of reach- 

 ing up to the corolla opening (Fig. 9, C). In the course 



FIG. 10. 

 Two primula flowers showing the extent of the small and of the large eye. 



of their experiments Bateson and Gregory crossed a large- 

 eyed homostyle plant with a small-eyed thrum (= short 

 style). The F l plants were all short styled with small 



