[Illustration: MANDIOCA PLANT.] "The plant has several names," said the Doctor, as they were walking to the garden; "the one most generally used is mandioca, but it is also called manioc, mandioc, yucca, and cassava, while its scientific appellation is _Jatropha manihot_. It is a native of South America, but has been introduced into Africa and other tropical countries, where it is extensively cultivated. There are two kinds of the plant; one is called the sweet cassava or sweet yucca, and its roots are eaten raw, but are more commonly roasted or boiled, and they are as nutritions as their South American brother, the potato. The other, which produces the tapioca of commerce and the mandioca flour of South America, contains a poison so deadly that thirty-five drops of it were sufficient to kill in six minutes a negro convicted of murder." "And this poisonous plant is used as an article of food?" Fred asked, in astonishment. "Yes. The juice contains hydrocyanic acid; but it is removed by pressure and by the action of heat, so that the dried flour is perfectly harmless. It is still a mystery how the unlettered Indians learned the virtues of the plant, which was in universal use when the Spaniards and Portuguese first came here. [Illustration: PLANTATION NEGRO.] "The Indians have a pretty fable concerning the origin of mandioca," the Doctor continued. "They say that long ago, in one of their tribes, a child was born which walked and talked precociously. It was named Mani, and died when it was only a year old. It was buried in the house where it died, according to the custom of the tribe; the roof of the building was removed, and the grave was watered daily. An unknown plant sprung from the grave; and when it ripened the earth cracked open and revealed the root. The Indians ate this root, and thus learned the uses of mandioca. Believing it to be the body of Mani, they gave it the name _Mani-oca_, the house of Mani." "A very pretty story, indeed," said Frank. "I will make a sketch of the plant in remembrance of it." By this time they had reached the garden, and Frank busied himself with his pencil, while Fred made note of the appearance of the bush, which was about five feet high, and had long, pointed leaves at the extremity of the branches. One of the plants was dug from the ground in their presence; the roots were in a cluster, and resembled large turnips, and the aggregate weight of the half-dozen roots that were taken out was from twenty-five to thirty pounds. In a shed close by a native was preparing the substance for use; the process may be thus described: