PLANTS CULTIVATED FOR THEIR SUBTERRANEAN PARTS. 57 



the sweet potato of whose cultivation the Portuguese 

 missionaries make mention. Thonning ^ does not name it. 

 Vogel brought back a species cultivated on the western 

 coast, which is certainly, according to the authors of 

 the Flora Nigritiana, Batatas panictUata of Choisy. It 

 was, therefore, a plant cultivated for ornamerit or for 

 medicinal purposes, for its root is purgative.^ It might 

 be supposed that in certain countries in the nld or new 

 world Ipomcea tuber osa, L., had been confounded with 

 the sweet potato; but Sloane^ teUs us that its enormous 

 roots are not eatable.* 



Ipomcea mammosa, Choisy (Convolvulus mamTnosus, 

 Loureiro ; Batata mammosa. Eumphius), is a Convol- 

 vulaceous plant with an edible root, which may well be 

 confounded with the sweet potato, but whose botanical 

 character is nevertheless distinct. This species grows 

 wild near Amboyna (Rumphius), where it is also culti- 

 vated. It is prized in Cochin-China. 



As for the sweet potato (Batatas edulis), no botanist, 

 as far as I know, has asserted that he found it wild him- 

 self, either in India or America.^ Clusius ^ atfirms upon 

 hearsay that it grows wild in the new world and in the 

 neighbouring islands. 



In spite of the probability of an American origin, 

 there remains, as we have seen, much that is unknown 

 or uncertain touching the original home and the trans- 

 port of this species, which is a valuable one in hot coun- 

 tries. Whether it was a native of the new or of the 

 old world, it is difficult to explain its transportation 

 from America to China at the beginning of our era, and 



* Schumaclier and Thonning, Beslc. Guin. 

 2 Wallich, in Eoxbnrorh, Fl. hid., ii. p. 63. 

 ' Sloane, Jam., i. p. 152. 



* Several Convolvnlacese have large roots, or more properly root- 

 stocks, but in this case it is the base of the stem with a part of the root 

 which is swelled, and this root-stock is always pnrgativp, as in the Jalap 

 and Turbith, while in the sweet potato it is the lateral roots, a different 

 organ, which swell. 



• No. 701 of Schomburgh, coll. 1, is wild in Guiana. According 

 to Choisy, it is a variety of the Batatas edulis ; according to Bentham 

 (Hook, Jour. Bot., v. p. 352), of the Batatas paniculata. My specimen, 

 which is rather imperfect, seems to me to be different from both. 



• Clusius, Hist., ii. p. 77. 



