ON THE INTERCROSSING OF INDIVIDUALS 111 



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 an- 

 other; but it must not be supposed that bees would thus pro- 

 duce 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 in- 

 variably and completely destroys, as has been shown by Gart- 

 ner, 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 con- 

 trivance 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 eflfec- 

 tually 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 beautiful and elaborate 

 contrivance by which all the infinitely 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 raise 

 plenty of seedlings. Another species of Lobelia, which is 

 visited by bees, seeds freely in my garden. In very many 

 other cases, though there is no special mechanical contrivance 

 to prevent the stigma receiving pollen from the same flower, 

 yet, as Sprengel, and more recently Hildebrand, and others, 

 have shown, and as I can confirm, either the anthers burst be- 

 fore the stigma is ready for fertilisation, or the stigma is 



