36 HETEROSTYLED DIMOKPHIC PLANTS. CHAP. L 



flowers before they were soaked in water were decidedly 

 broader, in proportion to their length, than those from 

 the long-styled ; after being soaked they were relatively 

 to those from the long-styled as 100 to 71 in diameter, 

 and more transparent. A large number of flowers from 

 the two forms were compared, and 12 of the finest 

 flowers from each lot were measured, but there was no 

 sensible difference between them in size. Nine long- 

 styled and eight short-styled plants growing together in 

 a state of nature were marked, and their capsules col- 

 lected after they had been naturally fertilised ; and 

 the seeds from the short-styled weighed exactly twice 

 as much as those from an equal number of long-styled 

 plants. So that the primrose resembles the cowslip in 

 the short-styled plants, being the more productive of 

 the two forms. The results of my trials on the fer- 

 tility of the two forms, when legitimately and illegi- 

 timately fertilised, are given in Table 9. 



We may infer from this table that the fertility of the 

 two legitimate unions taken together is to that of the 

 two illegitimate unions together, as judged by the pro- 

 portional 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 thus 

 differ remarkably from the same form of the cowslip, 

 which is quite sterile under the same circumstances. 

 Twenty-three spontaneously self-fertilised capsules from 



