with an extraordinary quantity of sugar, and it may either be
brought to the state of a honey-like sugar, or the juice pressed out
of the stalk, and fermented, forming the _pulque de mahio_, or _pulque
de Flaolli_, in Mexico[W].

Gum has been already stated to be the basis of all the other
organizable products, and it is found not only in almost all plants,
but in nearly all parts of them. In a pure or nearly isolated state,
it exists chiefly in the inner bark of vascular and especially
exogenous trees, and is preserved in the interior with the greatest
care: its escape externally results either from disease, as in the
case of plum and cherry-trees, from the puncture of insects, cracks in
the bark, or by artificial incisions. The death of the tree soon
follows the loss of this important juice, and thousands of trees of
the genus acacia are annually sacrificed in different parts of Africa
to procure the gum-arabic of commerce. It is only in a few genera and
tribes of trees, that it exists in so concentrated a state as to
assume the solid form on exposure to the air, but in some of these the
quantity is amazing. Hot countries are the chief abodes of such trees.
Thus, besides the immense quantity obtained from the acacias, the
_anacardium occidentale_ (cashew-nut tree) in America, has furnished
from a single tree a mass weighing forty-two pounds. Gum is mawkish,
insipid, and generally unpalatable, yet highly nutritive; and the
Africans, during the harvest of gum at Senegal, live entirely upon it,
eight ounces being the daily allowance for each man. In general they
become plump on this fare; and such should be the result, if the
calculation be correct, which assigns as great nutritive power to four
ounces of gum as to one pound of bread. This concentration of
nourishment renders gum a peculiarly suitable food for lengthened
journeys through the deserts, as it occupies small compass, and a
little suffices to stay the cravings of hunger. Thus, upwards of a
thousand persons may occupy more than two months in a journey from
Abyssinia to Cairo without any other kind of food[X]. Its bland,
demulcent properties fit it to correct the acrimony of the secretions
formed under the influence of a tropical sun and torrid air, with a
scanty and irregular supply of water. Plants, likewise, are preserved
in a vegetative and living state, mid sandy and arid wastes, by the
quantity of gum stored up in them. Hence succulent plants, such as
ca