48 HETEROSTTLED DIMORPHIC PLANTS. Chap. I. 



61.8 per cent, of seeds, in comparison, in each case, 

 with the legitimately fertilised flowers and capsules 

 of the same species. 



There is another point which deserves notice, 

 namely, the relative degree of infertility in the several 

 species of the long-styled and short-styled flowers, 

 when both are illegitimately fertilised. The data 

 may be found in the earlier tables, and in those given 

 by Mr. Scott in the Paper already referred to. If we 

 call the number of seeds per capsule produced by the 

 illegitimately fertilised long-styled flowers 100, the 

 seeds from the illegitimately fertilised short-styled 

 flowers will be represented by the following num- 

 bers : — 



We thus see that, with the exception of P. auricula, the 

 long-styled flowers of all nine species are more fertile 

 than the short-styled flowers, when both forms are il- 

 legitimately fertilised. Whether P. auricula really 

 differs from the other species in this respect I can form 

 no opinion, as the result may have been accidental. 

 The degree of self-fertility of a plant depends on two 

 elements, namely, on the stigma receiving its own pollen 

 and on its more or less efficient action when placed 

 there. Ifow, as the anthers of the short-styled flowers 

 of several species of Primula stand directly above the 

 stigma, their pollen is more likely to fall on it, or to 

 be carried down to it by insects, than in the case of 

 the long-styled form. It appears probable, therefore, 

 at flrst sight, that the lessened capacity of the short- 

 styled flowers to be fertilised with their own pollen, is 



