ato
starch than to any other fecula, but its particles are larger. Like
the other amylaceous substances, it forms a valuable and nutritious
article of food for the invalid.

The large tuberous roots of the Canna are equal in size to the human
head. The plant attains in rich soils a stature of fourteen feet, and
is identical, it is supposed, with the Achira of Choco, which has an
esculent root highly esteemed; and my friend, Dr. Hamilton, of
Plymouth, has named it provisionally, in consequence, _Canna achira_.
The starch of this root, he asserts, is superior to that of the
_Maranta_.

ROOT CROPS.

Amongst tuberous rooted plants, which serve as food for man in various
quarters of the globe, the principal are the common potato, yam,
cocoes or eddoes, sweet potatoes, taro, tacca, arrowroot, cassava, or
manioc, and the Apios (_Arracacha esculenta_). There are others of
less importance, which may be incidentally mentioned. The roots of
_Tropaeolum tuberosum_ are eaten in Peru, those of _Ocymum tuberosum_
in Java. In Kamschatka they use the root of the _Lilium Pomponium_ as
a substitute for the potato. In Brazil the _Helianthus tuberosus_. The
rhizomae and seed vessels of the Lotus form the principal food of the
aborigines of Australia. As a matter of curious information, I have
also briefly alluded to many other plants and roots, furnishing
farinaceous substance and support in different countries.

The comparative amount of human food that can be produced upon an acre
from different crops, is worthy of great consideration. One hundred
bushels of Indian corn per acre is not an uncommon crop. One peck per
week will not only sustain life, but give a man strength to labor, if
the stomach is properly toned to the amount of food. This, then, would
feed one man 400 weeks, or almost eight years! 400 bushels of potatoes
can also be raised upon an acre. This would give a bushel a week for
the same length of time; and the actual weight of an acre of sweet
potatoes (_Convolvulus batatas_) is 21,344 lbs., which is not
considered an extraordinary crop. This would feed a man (six pounds a
day) for 3,557 days, or nine and two-third years!

To vary the diet we will occasionally give rice, which has been grown
at the rate of 93 bushels to the acre, over an entire field. This, at
45 lbs. to the bushel, would be 4,185 lbs.; or, at 28 lbs. to the
bushel when husked, 2,604 lbs., which, at two pounds a day, would feed
a man 1,302 days, or