SOUTHERN PACIFIC LINES 179 
Desert conditions prevail all the way across southern Arizona, 
where the annual rainfall in the wide valleys is 10 inches or less. Most 
of the characteristic plants continue westward, notably the ubiquitous 
creosote bush, the mesquite, the yucca, the weird-looking ocotillo, 
and many cacti. On the adjoining mountains the rainfall is greater 
and there is a consequent difference in vegetation, and the higher 
summits carry extensive pine forests. The desert plants present 
many features of interest, especially in the flowering season, when 
some of them are of great beauty. On the lower rocky slopes grows 
the biznaga, or “barrel cactus” (Echinocactus wislizeni), with its 
large barrel-shaped body covered with curved thorns and bearing 
bright-red flowers in early summer. It contains much watery sap, 
which can be used to quench thirst very satisfactorily in case of neces- 
sity and has often been a life saver for man and beast. To obtain 
water the top is cut off and the liquid pressed out of the interior moe 
as shown in Plate 20, B. This pulp is also used in making candy. 
There are also the smaller Echinocactus johnsoni and clusters of the 
nigger-head cactus, E. polycephalus, which bears beautiful deep-red 
flowers in the early summer. All these cacti are covered with large 
spines and contain water which is protected f evapora- 
tion by the thick skin of the pa The desert rats, however, gnaw 
into some of them and clean out their watery pulp, lsaving an empty 
shell. The yellow-looking, very spiny, branching cactus (mostly 
Opuntia fulgida) begins to be conspicuous in the region west of Mescal 
and is a prominent member of the desert flora all across southwestern 
Arizona. 
Here also begins the sahuaro (Carnegiea gigantea), a treelike cactus 
with round fluted trunk which may reach a height of 50 feet; most of 
these strange plants bear branches that start high on the trunk and 
turn upward so as to produce the appearance of a giant candelabrum, 
as shown in Plate 31, B. The sahuaro is covered with thorns and in 
May bears at the top a cluster of white flowers, which in June develop 
into fruit that is in great favor with the Indians and birds. The 
Indians make from the fruit a kind of fig paste, also molasses, and an 
intoxicating drink. Garcés found the Indians greatly addicted to 
this drink at the time of his travels in 1775. Many birds make their 
nests in holes in the trunk, which they excavate in the soft pulpy 
material, but in a short time these cavities are sheathed with plant 
tissue which prevents sap leakage. It is stated by Spalding that most 
of these holes are made by the Gila woodpeckers (Melanerpes uropy- 
gialis), but they are utilized by other species, such as the sparrow 
hawk, screech owl, purple marten, and flycatcher. To this giant 
cactus the elf owl (Micrathene whitneyi) resorts when breeding; it is 
the smallest of owls, only a little larger than the humming bird. The 
gilded flicker is also fond of the sahuaro and rarely found elsewhere. 
