78 ORIGIN OF CULTIVATED PLANTS. 



L., and D. purpurea, Koxb., are cultivated in gardens, 

 Lut are not found wild. 



The Chinese yam, Dioscorea haiatas of Decaisne,' 

 extensively cultivated by the Chinese under the name 

 of Sain-in, and introduced by M. de Montigny into 

 European gardens, where it remains as a luxury, has 

 not hitherto been found wild in China. Other less- 

 known species are also cultivated by the Chinese, 

 especially the chou-yu, tou-tchou, chan-yu, mentioned 

 in their ancient works on agriculture, and which has 

 spherical rhizomes (instead of the pyriform spindles of 

 the B. batatas). The names mean, according to Stanis- 

 las Julien, mountain arum, whence we may conclude 

 the plant is really a native of the country. Dr. 

 Bretschneider ^ gives three Dioscorece as cultivated in 

 China (D. batatas, alata, sativa), adding, " The Dioscorea 

 is indigenous in China, for it is mentioned in the oldest 

 work on medicine, that of the Emperor Schen-nung." 



Dioscorea japonica, Thunberg, cultivated in Japan, 

 has also been found in clearings in various localities, 

 but Franchet and Savatier' say that it is not posi- 

 tively known to what degree it is wild or has strayed 

 from cultivation. Another species, more often cultivated 

 in Japan, grows here and there in the coimtry according 

 to the same authors. They assign it to Dioscorea 

 sativa of Linnseus; but it is known that the famous 

 Swede had confounded several Asiatic and American 

 species under that name, which must either be aban- 

 doned or restricted to one of the species of the Indian 

 Archipelago. If we choose the latter course, the true 

 D. sativa would be the plant cultivated in Ceylon with 

 which Linnaeus was acquainted, and which Thwaites 

 calls the D. sativa of Linnseus. Various authors admitted 

 the identity of the Ceylon plant with others cultivated 

 on the Malabar coast, in Sumatra, Java, the Philippine 

 Isles, etc. Blume * asserts that D. sativa, L., to which 



' Deoaisne, Uistoire et Cultwre de I'Igname de Chine, in the Bam 

 Ilorticole, 1st July and Deo. 1853 ; Flore des Serres et Jardins, x. pL 971. 

 ' On the Study and Value, eto.j p. 12. 

 ' Franchet and Savatier, Enum, Plant. JaponuB, ii, p. 47. 

 * Blame, Ewwn. Plant. Javas, p. 22. 



