86 ON THE INTERCROSSING 



and no doubt it is useful for this end : but the agency of 

 insects is often required to cause the stamens to spring for- 

 ward, as Kolreuter has shown to be the case with the bar- 

 berry ; 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 numerous other cases, far from 

 self-fertilization being favored, 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 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 flow T er 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 

 before the stigma is ready for fertilization, or the stigma is 

 ready before the pollen of that flower is ready, so that these 

 so-named dichogamous plants have in fact separated sexes, 

 and must habitually be crossed. So it is with the recipro- 

 cally dimorphic and trimorphic plants previously 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 be in so many cases mutually useless to each other ! 

 How simply are these facts explained on the view of an 

 occasional cross with a distinct individual being advantageous 

 or indispensable ! 



If several varieties of the cabbage, radish, onion, and of 

 some other plants, be allowed to seed near each other, a 

 large majority of the seedlings thus raised turn out, as I 

 found, mongrels : for instance, I raised 233 seedling cab- 

 bages from some plants of different varieties growing near 

 each other, and of these only 78 were true to their kind, and 

 some even of these were not perfectly true. Yet the pistil 



