NATURAL SELECTION 89 



and then the stigma of another with the same brush 

 to ensure fertilisation ; but it must not be supposed 

 that bees would thus produce a multitude of hybrids 

 between distinct species ; for if you bring on the same 

 brush a plant's own pollen and pollen from another 

 species, the former will have such a prepotent effect, 

 that it will invariably and completely destroy, as has 

 been shown by Gartner, any influence from 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 contri- 

 vance 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 many other cases, 

 far from there being any aids for self- fertilisation, 

 there are special contrivances, as I could show from 

 the writings of C. C. Sprengel and from my own 

 observations, which effectually prevent the stigma 

 receiving pollen from its own flower : for instance, 

 in Lobelia fulgens, there is a really beautiful and 

 elaborate contrivance by which every one of the infin- 

 itely numerous pollen -granules are swept out of the 

 conjoined anthers of each flower, before the stigma of 

 that individual flower is ready to receive them ; and as 

 this flower is never visited, at least in my garden, by 

 insects, it never sets a seed, though by placing pollen 

 from one flower on the stigma of another, I raised 

 plenty of seedlings ; and whilst another species of 

 Lobelia growing close by, which is visited by bees, 

 seeds freely. In very many other cases, though there 

 be no special mechanical contrivance to prevent the 

 stigma of a flower receiving its own pollen, yet, as 

 C. C. Sprengel has shown, and as I can confirm, either 



