440 



In the wetter regions of the Xigerian coast and adjacent parts, 

 the Yellow Guinea Yam gets some of the importance of the White 

 Guinea Yam; because as it grows through the whole year, never 

 resting, it is peculiarly suited to those equitable parts, and the 

 tubers can to a certain extent lae dug as wanted. These tubers will 

 not keep. It has not got the same great number of races that the 

 White Guinea 3'^am has. 



Both the Whit.e and the Yellow Guinea yams were early taken 

 to the Xew World, as also was the Indi-au D. alaid, — whether for 

 the first time independently of the slave trade, or in the course of 

 that trade cannot now be ascertained; l>ut this is well atte.ted, that 

 yams were shipped with the negroes as provisions for the 

 voyage whetlier to Lislwn for ])roceeding thence to America or to 

 America direct: and among the various names .applied to them 

 in the West Indies to this day are certain distinctly reminiscent 

 of the custom, such as Xegro Yam, Guinea Yam and Lisibon Yam. 

 The proper application of these names would seem to*be, Xegro Yam 

 to the White Guinea Yam, Guinea Yam to the Yellow Guinea 

 Yam. and Lisbon Yam to certain races of D. alatit, but there are 

 inconsistencies in modern usage. The last named was probably m 

 West Africa before it was in America, for Marcgraf writing in 

 1648 called it the Iidiame de S. Thome or Yam of St. Thomas' 

 island, the said island being off tlie Gaboon coast. 



Because of their keeping qualities, the White Guinea Yam and 

 D. alata were better for provisioning ships th-an the Yellow Guinea 

 yam ; but the last had the advantage of being available almost 

 through the year. The three kept a proportionate importance in 

 the West Indies, and nothing could l)e more natural than that 

 botanists should make acquaintance with them, though tw^o are 

 African, in America. Thus it happened that Lamarck in 1789 

 ■described the Yellow' Guinea Yam from Guiana under the name of 

 Dioscorca cayenensis, and Poiret in 1813 described from a West 

 Indian specimen a D. rofunddia. Avhich as far as his inadequate 

 material and incomplete description show, can be considered a> the 

 White Guinea Yam. The description not sufficing for a clear 

 understanding, Grisebach in his Flora of the British West Indies, 

 1864, p. 587, set dowai the latter as a variety of the former, 

 a place which it has occupied since, and in which Sir David 

 Prain and the writer left it, when discussing in the Kew Bulletin 

 1919, p. 364, Dioscorea sativa. But subsequently the photographs 

 here reproduced, of types of both names, as they exist in Desfon- 

 taines' herbarium,, were obtained, and in correspondence between 

 Professor E. Chiovenda, who has charge of that Herbarium. Sir 

 T)avid Praii'i and the writer, the conchisions have been reached that 

 Poiret had l^efore him a branch of the AATiite Guinea Yam when he 

 drew up his description of D. rotundata. and tliat therefore, no 

 older name existing, the "White Guinea Yam is to be so called. 



The identity of the Yellow Guinea Yam with D. cayencnsis, 

 Lamk.. has been asserted already by Dr. August Chevalier in the 

 Bulletin de la Societe hotanique de France, IX, 48, fig. 3 bis. where 



