On the other hand, there are arguments in favour of an Asiatic origin. The Chinese _Encyclopædia of Agriculture_ speaks of the sweet potato, and mentions different varieties;[153] but Bretschneider[154] has proved that the species is described for the first time in a book of the second or third century of our era. According to Thunberg,[155] the sweet potato was brought to Japan by the Portuguese. Lastly, the plant cultivated at Tahiti, in the neighbouring islands, and in New Zealand, under the names _umara_, _gumarra_, and _gumalla_, described by Forster[156] under the name of _Convolvulus chrysorhizus_, is, according to Sir Joseph Hooker, the sweet potato.[157] Seemann[158] remarks that these names resemble the Quichuen name of the sweet potato in America, which is, he says, _cumar_. The cultivation of the sweet potato became general in Hindustan in the eighteenth century.[159] Several popular names are attributed to it, and even, according to Piddington,[160] a Sanskrit name, _ruktalu_, which has no analogy with any name known to me, and is not in Wilson’s Sanskrit Dictionary. According to a note given me by Adolphe Pictet, _ruktalu_ seems a Bengalee name composed from the Sanskrit _alu_ (_Rukta_ plus _âlu_, the name of _Arum campanulatum_). This name in modern dialects designates the yam and the potato. However, Wallich[161] gives several names omitted by Piddington. Roxburgh[162] mentions no Sanskrit name. Rheede[163] says the plant was cultivated in Malabar, and mentions common Indian names. The arguments in favour of an American origin seem to me much stronger. If the sweet potato had been known in Hindustan at the epoch of the Sanskrit language it would have become diffused in the old world, since its propagation is easy and its utility evident. It seems, on the contrary, that this cultivation remained long unknown in the Sunda Isles, Egypt, etc. Perhaps an attentive examination might lead us to share the opinion of Meyer,[164] who distinguished the Asiatic plant from the American species. However, this author has not been generally followed, and I suspect that if there is a different Asiatic species it is not, as Meyer believed, the sweet potato described by Rumphius, which the latter says was brought from America, but the Indian plant of Roxburgh.