Chap. I. PEIMULA VEEIS. 31 



this whole subject I shall recur. No doubt pollen will 

 occasionally be placed by insects or fall on the stigma 

 of the same flower ; and if cross-fertilisation fails, such 

 self-fertilisation will be advantageous to the plant, as 

 it will thus be saved from complete barrenness. But 

 the advantage is not so great as might at first be 

 thought, for the seedlings from illegitimate unions do 

 not generally consist of both forms, but all belong to 

 the parent form ; they are, moreover, in some degree 

 weakly in constitution, as will be shown in a future 

 chapter. If, however, a flower's own pollen should first 

 be placed by insects or fall on the stigma, it by no 

 means follows that cross-fertilisation will be thus pre- 

 vented. It is well known that if pollen from a distinct 

 species be placed on the stigma of a plant, and some 

 hours afterwards its own pollen be placed on it, the 

 latter will be prepotent and will quite obliterate any 

 effect from the foreign pollen ; and there can hardly 

 be a doubt that with heterostyled dimorphic plants, 

 pollen from the other form will obligate the effects of 

 pollen from the same form, even when this has been 

 placed on the stigma a considerable time before. To 

 test this belief, I placed on several stigmas of a long- 

 styled cowslip plenty of pollen from the same plant, 

 and after twenty-four hours added some from a short- 

 styled dark-red polyanthus, which is a variety of the 

 cowslip. From the flowers thus treated 30 seedlings 

 were raised, and all these, without exception, bore 

 reddish flowers ; so that the effect of pollen from the 

 same form, though placed on the stigmas twenty-four 

 hours previously, was quite destroyed by that of pollen 

 from a plant belonging to the other form. 



Finally, I may remark that of the four kinds of 

 unions, that of the short-styled illegitimately fertilised 

 with its own-form pollen seems to be the most sterile of 



