28 HETEEOSTYLBD DIMOEPHIC PLANTS. Chap. L 



have been combined by giving the average number of 

 seeds produced by all the flowers which were fertilised, 

 whether they yielded capsules or not; but I have 

 thought that it would be more instructive always to 

 show separately the proportion of flowers which pro- 

 duced capsules, and the average number of apparently 

 good seeds which the capsules contained. 



Flowers legitimately fertilised set seeds under con- 

 ditions which cause the almost complete failure of 

 illegitimately fertilised flowers. Thus in the spring of 

 1862 forty flowers were fertilised at the same time in 

 both ways. The plants were accidentally exposed in 

 the greenhouse to too hot a sun, and a large number 

 of umbels perished. Some, however, remained in mo- 

 derately good health, and on these there were twelve 

 flowers which had been fertilised legitimately, and 

 eleven which had been fertilised illegitimately. The 

 twelve legitimate unions yielded seven fine capsules, 

 containing on an average each 57 • 3 good seeds ; whilst 

 the eleven illegitimate unions yielded only two cap- 

 sules, of which one contained 39 seeds, but so poor, 

 that I do not suppose one would have germinated, and 

 the other contained 17 fairly good seeds. 



From the facts now given the superiority of a legi- 

 timate over an illegitimate union admits of not the 

 least doubt; and we have here a case to which no 

 parallel exists in the vegetable or, indeed, in the 

 animal kingdom. The individual plants of the pre- 

 sent species, and as we shall see of several other 

 species of Primula, are divided into two sets or 

 bodies, which cannot be called distinct sexes, for 

 both are hermaphrodites ; yet they are to a certain 

 extent sexually distinct, for they require reciprocal 

 union for perfect fertility. As quadrupeds are di- 

 vided into two nearly equal bodies of different sexes, 



