Chap. IV. On the Intercrossing of Individuals. jy 



what a multitude of flowers have their anthers and stigmas fully 

 exposed to the weather ! If an occasional cross be indispensable, 

 notwithstanding that the plant's own anthers and pistil stand so 

 near each other as almost to ensure self-fertilisation, the fullest 

 freedom for the entrance of pollen from another individual will 

 explain the above state of exposure of the organs. Many flowers, 

 on the other hand, have their organs of fructification closely 

 enclosed, as in the great papilionaceous or pea-family ; but these 

 almost invariably present beautiful and curious adaptations in 

 relation to the visits of insects. So necessary are the visits of bees 

 to many papilionaceous flowers, that their fertility is greatly dimi- 

 nished if these visits be prevented. Now, it is scarcely possible for 

 insects to fly from flower to flower, and not to carry pollen from 

 one to the other, to the great good of the plant. Insects act like a 

 camel-hair pencil, and it is sufficient, to ensure fertilisation, just to 

 touch with the same brush the anthers of one flower and then the 

 stigma of another ; but it must not be supposed that bees would 

 thus produce a multitude of hybrids between distinct species ; for if 

 a plant's own pollen and that from another species are placed on 

 the same stigma, the former is so prepotent that it invariably and 

 completely destroys, as has been shown by Gartner, the influence 

 of the foreign pollen. 



: ? When the stamens of a flower suddenly spring towards the pistil 

 or slowly move one after the other towards it, the contrivance 

 seems adapted solely to ensure self-fertilisation; and no doubt it is 

 useful for this end: but the agency of insects is often required to 

 cause the stamens to spring forward, as Kolreuter has shown to be 

 the case with the barberry ; and in this very genus, which seems to 

 have a special contrivance for self-fertilisation, it is well known 

 that, if closely-allied forms or varieties are planted near each other 

 it is hardly possible to raise pure seedlings, so largely do they 

 naturally cross In numerous other cases, far from self-fertilisation 

 being favoured, there are special contrivances which effectually 

 prevent the stigma receiving pollen from its own flower, as I could 

 show from the works of Sprengel and others, as well as from my 

 own observations : for instance, in Lobelia fulgens, there is a really 

 b dutiful and elaborate contrivance by which all the infinitely 

 numerous poden-granules are swept out of the conjoined anthers of 



reel r^ >r ' bef0r V lie Stigma 0f that ^dividual flower is ready to 

 i"»re them ; and as this flower is never visited, at least in my 



Ci one flnr eCtS ' « ™™ Bet8 * ^ thoi ^ h h ? P lacin S Pollen 



■:° n i° n the st §? a ^ another, I raised plenty of seed- 



im e s. Another species of Lobelia, which is visited by bees, seeds 



