PLANTS CULTIVATKD FOR THEIK SUBTERRANEAN PARTS. 61 



much sap, are not good to eat, and would cause positive 

 harm to persons who consumed any quantity of them. 

 All potatoes, and probably all maniocs, contain something 

 harmful, which is observed even in the products of dis- 

 tillation, and which varies with several causes ; but only 

 matter foreign to the fecula should be mistrusted. 



The doubts about the number of species into which 

 the cultivated manihots should be divided are no source 

 of difficulty regarding the question of geographic origin. 

 On the contrary, we shall see that they are an important 

 means of proving an American origin. 



The Abbs? Raynal had formerly spread the erroneous 

 opinion that the manioc was imported into America from 

 Africa. Robert Brown ^ denied this in 1818, but without 

 giving reasons in support of his opinion ; and Humboldt,^ 

 Moreau de Jonnes,^ and Saint Hilaire * insisted upon its 

 American origin. It can hardly be doubted for the 

 following reasons : — 



1. Maniocs were cultivated by the natives of Brazil, 

 Guiana, and the warm region of Mexico before the arrival 

 of the Europeans, as all early travellers testify. In the 

 West Indies this cultivation was, according to Acosta,' 

 common enough in the sixteenth century to inspire the 

 belief that it was also there of a certain antiquity. 



2. It is less widely diffused in Africa, especially in 

 regions at a distance from the west coast. It is known 

 that manioc was introduced into the Isle of Bourbon by 

 the Governour Labourdonnais.^ In Asiatic countries, 

 where a plant so easy to cultivate would probably have 

 spread had it been long known on the African continent, 

 it is mentioned here and there as an object of curiosity 

 of foreign origin.' 



' R. Brown, Botcmy of ihe Congo, p. 50. 



' Humboldt, Nouvelle Espagrie, edit. 2, vol. ii. p. 398. 



' Hist, de I' Acad, des Sciences, 1824. 



' Gaillemin, Archives de Botanique, i. p. 239. 



' AcoBta, Hist. Nat. des Indes, French trans., 1598, p. 163. 



• Thomas, Statistique de Bourbon, ii. p. 18. 



' The catalogae of the botanical gardens of Baitenzorg, 1866, p. 222, 

 sajs expressly that the Manihot utilissima comes from Bourbon and 

 America. 



