they
present an appearance scarcely less attractive than the saguaro.

[Illustration: FIG. 86.--OCATILLA]

Scattered among the vegetation just mentioned is the palo verde
(green tree), so named from the yellowish green of its bark. It is
remarkable for the small size of the leaves, which afford scarcely
any shade for the traveller upon a hot summer day. (Fig. 84.)

Along the dry water courses we find the mesquite, a tree which does
not grow upon the gravelly plains and rocky slopes, for it needs
more moisture than most of the desert vegetation. In the spring
it puts out delicate green leaves which form a pleasing contrast
with the other plants.

Riding through one of these forests in the deepening twilight,
one is impressed with a feeling of awe and mystery by the strange,
weird shapes outlined against the sky. In the cooler air of evening
the animals come from their retreats. The insects and the snakes are
then abroad, and if one is on foot the sudden buzz of a rattlesnake
is not a pleasant sound to hear.

[Illustration: FIG. 87.--MESQUITE TREE, SANTA CRUZ VALLEY, SOUTHERN
ARIZONA]

The prickly-pear prefers slopes not quite so dry and hot as those
of the forest just described. Its broad, spade-like, jointed stems
are very interesting. The red fruit clustered upon their extremities
is not disagreeable to the taste, but is covered with a soft, prickly
down.

Associated with the prickly-pear is a species of agave, but this
does not grow so large in Arizona as it does farther south in Mexico.
The plant is familiar to us as the common century plant of our
gardens. The long fleshy leaves with spines at the ends are clustered
at the surface of the ground, and from their centre, at blooming
time, rises a tall flower stalk. The agave requires many years to
mature. When the flower stalk has once started it grows rapidly,
but after blossoming the plant dies.

The mezcal, or pulque, the national drink of the Mexicans, is made
from the sap of the agave. The fibre of the agave, known as sisal
hemp, is used in the manufacture of rope, twine, mats, brushes,
etc. Other parts of the plant have various uses.

[Illustration: FIG. 88.--THE AGAVE]

[Illustration: FIG. 89.--SPANISH BAYONET IN BLOOM]

There are many kinds of yucca in the more elevated portions of
the desert. They range in size from those only two or three feet
high, of which the Spanish bayonet is a type, to the giant yucca of
the Mohave Desert, which attains