52 



MEN DEL ISM 



large. Besides the normal long and short styled 

 forms, there occurs a third form, which has been 

 termed homost)-le. In this form the anthers are 

 jilaccd low down in the corolla tube as they are in 

 the long-st)-led form, but the st}'le remains short 

 instead of reaching up to the corolla opening (Fig. 

 9, C). In the course of their experiments Bateson 



Fig. 10. 



Tuo primula flowers showing the extent of the sniall jrrd of the large eye. 



and Gregory crossed a large-eyed homostyle plant 

 with a small-eyed thrum ( = short style). The F^ 

 plants were all short styled with small eyes. On 

 self-fertilisation these gave an F., generation consist- 

 ing of four types, viz. short styled with small eyes, 

 short styled with large eyes, long styled with small 

 eyes, and homostylcd with large eyes. The notable 

 feature of this generation is the appearance of long- 

 styled plants, which, however, occur only in associa- 

 tion with the small eye. The proportions in which 

 these four types appeared shows that the presence 

 or absence of but two factors is concerned, and at 



