ON THE MIGRATION OF CULTIVATED PLANTS. 831 
is still to be found in its wild state. The plant is a slender creeper, 
yielding a huge tuber, often weighing from ten up to thirty pounds, 
consisting of a great mass of farinaceous matter, a wholesome but dry 
and insipid food, greatly inferior in flavour to the common, or even to 
the sweet, Potato. 
The Sweet Potato, or Batata (Batatas edulis), is, like the Yam, the 
plant of a warm climate. It is a native of the tropical parts of both 
Asia and America, but is stated not to have been an object of cultiva- 
tion by the native Americans, the first mention of it being by Riga- 
fetta, the companion of Magellan, in the first quarter of the fifteenth 
century. In the neighbourhood of the equator, the Batata grows to a 
large size, often weighing several pounds; in Java, I have myself seen 
them of ten pounds weight, and occasionally they are said to reach 
even to fifty. In that island they enter largely into the food of the 
people,—never, however, forming their principal vegetable diet, which 
is always rice. 
One or more species of the genera Ocimum, Arum, Caladium, Ma- 
ranta, Tacca, and Jatropha yield esculent roots, which, in a rude state of 
society, in their respective native countries, were the only bread of the 
people before the culture of the cerealia began. Their starch, in a 
refined state, comes to us under the names of arrowroot, tapioca, cas- 
sava, salep, ete. The plants yielding these productions are, with few 
exceptions, natives of tropical or, at least, of very warm countries. 
Some of them, in their erude and unprepared state, are either poisonous 
or acrid, but the savage cultivators had everywhere discovered that 
heat or edulcoration dissipated the poison, and rendered them whole- 
some food. 
The Taro, or Caladium esculentum, formed the principal bread of all 
the South-Sea Islanders, who had no kind of corn; and the Manioe, or 
Jatropha Manihot, that of the rude inhabitants of native America, who 
had but one of the cereals, and even that one not universally known 
and cultivated. 
e Breadfruit (Artocarpus incisa), in so far as concerns its use as 
bread, is confined to the tropical islands of the Pacific, to the inhabi- 
tants of which it formed a considerable article of diet, and, no doubt, 
contributed materially to the social advancement at which they had 
arrived when first seen by Europeans. At the recommendation of 
some theoretical botanists, the tree was conveyed, in 1792, at great 
VOL. Iv. [OCTOBER 1, 1866. - 
