462 Mr. C. Darwin on the Agency of Bees 



doctrine that no plant self-fertilizes itself for a perpetuity of 

 generations. After pretty close investigation of the subject, I 

 am strongly inclined to believe that this is a law of nature 

 throughout the vegetable and animal kingdoms. I am well 

 aware that there are several cases of difficulty. 



The Leguminosse with papilionaceous flowers have been ad- 

 vanced by Pallas and others as a case in which crossing could 

 never naturally take place. But any plant habitually visited by 

 insects in such a manner that their hairy bodies, to which pollen 

 so readily adheres, come into contact with the stigma, could 

 hardly fail occasionally to receive the pollen from another in- 

 dividual of the same species. In all LeguminosEe, bees do brush 

 over the stigma. And the possibility of crossing would be very 

 strong in the case of any plant, if the agency of insects were 

 necessary for its self-fertilization ; for it would show that it was 

 habitually visited by them. 



From these considerations I was led to believe that papilio- 

 naceous plants must be occasionally crossed. Nevertheless I must 

 confess that, from such evidence as I have been able to acquire, 

 crossing between varieties growing close together does not take 

 place nearly so freely as I should have expected. As far as I 

 am aware, only three or four cases of such crosses are on record. 

 It is not by any means, I believe, a common practice with seed- 

 raisers to keep the crops of their leguminous plants separate. 

 Hence I was led last year, in my short communication to the 

 ' Gardeners' Chronicle/ to ask whether any of your readers had 

 any experience on the natural crossing of Beans, Peas, &c. Mr. 

 Coe, of Knowle, near Fareham, Hants, in the most obliging man- 

 ner sent me some specimens, and an account that last summer he 

 had planted four rows of the Negro Dwarf Kidney Bean between 

 some rows of the white and brown dwarfs, and likewise near 

 some Scarlet Runners. The dwarfs he had saved for seed. The 

 plants themselves he believes presented nothing remarkable in 

 foliage, height, flowers, &c. ; and he feels sure that their pods 

 were all alike : but the beans themselves presented an extraor- 

 dinary mixture, as I can testify from the sample sent me, of all 

 shades between light brown and black, and a few mottled with 

 white ; not one-fifth of the beans, perhaps much less, were pure 

 Negroes. Some few of the beans also in the rows of the white 

 Haricot were affected, but none of the brown dwarfs. 



Hence, then, we apparently have the extraordinary fact, de- 

 scribed by Wiegmann in the case of several leguminous plants 

 experimented on most carefully by Gartner in the case of the 

 Pea, and described a few years ago by Mr. Berkeley in the l Gar- 

 deners' Chronicle/ of the pollen of one variety having affected 

 not only the embryo but the tunics of the seed borne by the pure 



