PLANTS CULTIVATED FOR THEIR SUBTERRANEAN PARTS. 57 



the sweet potato of wliose cultivation the Portuguese 

 missionaries make mention. Thonning ^ does not name it. 

 Vogel brought back a species cultivated on the western 

 coa.st, which is certainly, according to the authors of 

 the Flora Nigritiana, Batatas panictdata of Choisy. It 

 was, therefore, a plant cultivated for ornament or for 

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

 be supposed that in certain countries in the nld or new 

 world Ipomcea tuherosa, L,, had been confounded with 

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

 roots are not eatable.* 



Ijyomoia raanfirriosa, Choisy {Convolvulus mammosus, 

 Loureiro ; Batata mammosa, Rumphius), 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 (BataJas edulis), no botanist, 

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

 self, either in India or America.^ Clusius ^ affirms 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 Roxburgh, Fl. Ind., ii. p. 63. 

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



* Several Convolvulaceae 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 purgative, 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 Gniana. According 

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

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

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



* Clusius, Hist., ii. p. 77. 



