100 INTEKCEOSSING OF INDIVIDUALS. Ca.vp. IV. 



insure fertilization ; but it must not be supposed that bees 

 would thus produce a multitude of hybrids between distinct 

 species ; for if you brinf^ on the same brush a plant's own pol- 

 len and pollen from another species, the former will have such 

 a prepotent effect, that it will invariably and completely de- 

 stroy, as has been shown by Gartner, any influence from the 

 foreig'n pollen, 



^V'hen the stamens of a flower suddenly spring toward the 

 pistil, or slowly move one after the other toward it, the con- 

 trivance seems adapted solely to insure self-fertilization ; 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 Kol- 

 reutcr has shown to be the case with the barberry ; and in this 

 very genus, which seems to have a special contrivance for self- 

 fertilization, 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-fertili- 

 zation, 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 all the infinitely 

 numerous pollen-granules are swept out of the conjoined an- 

 thers 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, b}^ insects, it never sets a seed, though by 

 placing pollen from one flower on the stigma of another, I 

 raised plenty of seedlings ; and while another species of Lobe- 

 lia growing close by, which is visited by bees, seeds freely. 

 In very many other cases, though there be no special mechani- 

 cal 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 the anthers burst before the stigma is ready for 

 fertilization, or the stigma is ready before the pollen of that 

 flower is ready, so tliat these plants have in fact separated 

 sexes, and nnist habitually be crossed. So it is with the recip- 

 rocally dimorphic and trimorphic plants pre\dously alluded to. 

 How strange are these facts ! How strange that the pollen 

 and stigmatic surface of the same flower, though placed so 

 close together, as if for the very purpose of self-fertilization, 

 should in so many cases be nuitually useless to each other! 

 Hov>' simjily are these facts explained on the view of an oeca- 



