ided
with fleshy stems which hold a supply of moisture to be drawn upon
during the long dry season. Men and animals are sometimes saved from
death by chewing the pulp of the prickly-pear or other cactuses.
After a period of exceptional drought, the stems of the prickly-pear
lose their bright green color and become shrunken.

[Illustration: FIG. 81.--PRICKLY-PEAR, BALL CACTUS, AND SPANISH
BAYONET]

The development of the underground part of the plant is frequently
out of all proportion to the part above the surface. The manzanita,
which grows in the semi-arid climate of southern California, is
a low shrub with branches that are rarely large enough for fuel.
The roots, however, are large and massive, and are extensively
used for firewood.

The desert plants are armed, not only against the dry air, but
against the wandering animals which would bite them and suck their
juices. The smell of the sagebrush is such that very few animals
will touch it. Other plants are protected by thorns. In fact, the
drier the region, the more thorny are its plants. A little shrub
called the crucifixion thorn has no leaves at all, nothing but
long, sharp spines. Besides the straight thorns there are curved
and also barbed ones, for every conceivable form is represented
among the plants of these dry lands.

As the desert plants are armed against the animals, so the animals
are armed against each other. Many of the insects and reptiles
are extremely poisonous; the greater the heat of their habitat,
the more dangerous are their bites. The horned toad, while not
poisonous, is protected by having horny spines upon its head and
back. The little rattlesnake known as the "side-winder" is perhaps
the most dangerous of all, although the tarantula, centipede, and
scorpion are formidable foes. The Gila monster, long believed to
be so dangerous, is now considered non-poisonous under ordinary
conditions.

[Illustration: FIG. 82.--CRUCIFIXION THORN]

The desert tortoise is perhaps the most remarkable of all the animals
of the desert. It is rare, and little is known of its habits except
that it lives in the most arid valleys of southeastern California,
far removed from any water. This tortoise has a diameter across
its shell of at least eighteen inches. Its flesh is much prized
by the Indians and prospectors. A specimen which had been without
water for an indefinite period was dissected, and the discovery
was made that upon each side there was a mem