Chap. I. PRIMULA VUXGAEIS. 37 



the two illegitimate unions taken together, as judged by 

 the proportional number of flowers which when fertilised 

 in the two methods yielded capsules, as 100 to 60. If we 

 judge by the average number of seeds per capsule pro- 

 duced by the two kinds of unions, the ratio is as 100 

 to 54; but this latter figure is perhaps rather too low. 

 It is surprising how rarely insects can be seen during the 

 day visiting the flowers, but I have occasionally observed 

 small kinds of bees at work; I suppose, therefore, that 

 they are commonly fertilised by nocturnal Lepidoptera. 

 The long-styled plants when protected from insects 

 yield a considerable number of capsules, and they thua 

 differ remarkably from the same form of the cowslip, 

 which is quite sterile under the same circumstances. 

 Twenty-three spontaneously self-fertilised capsules from 

 this form contained, on an average, 19.2 seeds. The 

 short-styled plants produced fewer spontaneously self- 

 fertilised capsules, and fourteen of them contained only 

 6.3 seeds per capsule. The self -fertilisation of both 

 forms was probably aided by Thrips, which abounded 

 within the flowers ; but these minute insects could not 

 have placed nearly sufficient pollen on the stigmas, as 

 the spontaneously self-fertilised capsules contained 

 much fewer seeds, on an average, than those (as may be 

 seen in Table 9) which were artificially fertilised with 

 their own-form pollen. But this difference may perhaps 

 be attributed in part to the flowers in the table having 

 been fertilised with pollen from a distinct plant be- 

 longing to the same form; whilst those which were 

 spontaneously self-fertilised no doubt generally received 

 their own pollen. In a future part of this volume some 

 observations will be given on the fertility of a red- 

 coloured variety of the primrose. 



