KunzE: THE DESERT FLORA OF PHOENIX, ARIZONA 305 
two feet long, weighing from ten to fifteen pounds each. It will 
do best in a very sandy loam. Natives make use of this root 
for burns and other inflamed surfaces, cutting off a slice from a 
growing plant, and applying it to the affected parts. The stems 
do not grow very long, from two to four feet at most. Usually 
these plants grow under a mesquit tree or beside a tall sagebrush, 
to shelter the slender stem from the force of our wind or sand- 
storms. The stem is from one half to one inch thick, four- or five- 
angled, bluish-green and short-spined. I obtained fruit by cross- 
fertilization in the garden. 
Other striking plants of our desert are two species of “ palo 
verde,” of which one is Parkinsonia microphylla, scattered all over 
the barren soil, and growing out of crevices of the rock like a 
succulent. It is not a large tree, and being hard in texture, it is 
much used for firewood. The leaves appear late in autumn or after 
the winter rains, and drop in April, when the tree is covered by 
panicles of yellow flowers, attracting many insects. The hard 
seeds are shelled out by birds, and the bark is gnawed off by the 
lemur-like desert squirrels and rodents. The pinnate leaves of 
this species have leaflets not larger than the head of a pin. This 
tree grows on the mesa as well as on mountains. 
Parkinsonia Torreyana is a much handsomer tree, and its leaves, 
much larger than those of the preceding species, also appear at the 
approach of winter. The branches are more graceful; they are 
pendant, and when covered by the large yellow panicles of flowers 
early in April present a gorgeous appearance. This species affects 
the arroyos or watercourses more than the other. Young trees 
are quite bushy in shape. The branches of all Parkinsonias are 
prickly. The seeds of P. Zorreyana furnish food for birds, and its 
flowers bread for bees. 
Acacia Greggtt is another very prickly desert bush, which in 
sheltered situations retains its small leaves all winter. In May it is 
covered by small, yellow, fragrant flowers furnishing fine bee-food. 
The branches having hooked thorns, it is known as the cat-claw 
acacia, and is much dreaded. It bears twisted brown flat pods. 
Its height is from five to ten feet. 
Covillea Mexicana, or creosote bush, is the commonest ever- 
green shrub of the cactus desert, growing from four to ten feet 
