PLANTS CULTIVATED FOR THEIR SUBTERRANEAN PARTS. 49 



say of its introduction from the Iberian peninsula, it is 

 not at all likely that the Italians had any dealings with 

 Raleigh's companions. 



No one can doubt that the potato is of American 

 origin ; but in order to know from what part of that 

 vast continent it was brought, it is necessary to know 

 if the plant is found wild there, and in what localities. 



To answer this question clearly, we must first remove 

 two causes of error : the confusion of allied species of the 

 genus Solanum with the potato ; and the other, the 

 mistakes made by travellers as to the wild character 

 of the plant. 



The allied species are Solanum Commersonii of 

 Dunal, of which I have already spoken; S. inaglia 

 of Molina, a Chili species; S. immite of Dunal, a 

 native of Peru ; and >S'. verrttcosum ^ of Schlechtendal, 

 which OTows in IMexico. These three kinds of Solanum 

 have smaller tubers than S. tuberosum, and differ also 

 in other characteristics indicated in special works on 

 botany. Theoreticall}", it may be believed that all these, 

 and other forms growing in America, are derived from a 

 single eailier species, but in our geological epoch they 

 present themselves with differences which seem to me to 

 justify specific distinctions, and no experiments have 

 proved that by crossing one with another a product 

 would be obtained of which the seed (not the tubers) 

 would propagate the race. Leaving these more or less 

 doubtful questions of species, let us tiy to ascertain 

 whether the common form of Solanum tuberosum has been 

 found wild, and merely remark that the abundance of 

 tuberous solanums growing in the temperate regions of 

 America, from Chili or Buenos Ay res as far as Mexico, con- 

 firms the fact of an American origin. If we knew nothing 

 more, this would be a strong presumption in favour of 

 this country being the original home of the potato. 



The second cause of error is very clearly explained 



* Solanum. verrucosum, whose introduction into the neighbourhood 

 of Gex, near Geneva, I mentioned in 1855, has since been abandoned 

 because its tubers are too small, and because it does not, as it was hoped, 

 withstand the potato-fungus. 



