304 BAILEY: THE WILD COTTON PLANT IN ARIZONA 
plants, but giant cactus and sotol occupy slightly different expo- 
sures in such close proximity as to appear all mixed up. Mr. 
Hudson marked the range of Thurberia along this section on the 
contour map, bringing it down to about 2,500 feet in places on the 
canyon sides but showing most of the range to be on dry slopes and 
mesa tops at about 3,000 feet. This region is so exceedingly 
rough and broken that the zones are hopelessly mixed and run 
abnormally high and low. 
The plant has been collected in several other mountain ranges 
but many of the records are so indefinite as to be of little use in 
defining its zonal range. Professor Thornber showed me specimens 
from the Rincon Mountains (Manning Trail), the Mule Mountains, 
Dragoon Summit and Fort Bowie. In the National Herbarium 
there are specimens from the Rincon Mountains at 4,500 feet 
altitude, Davidson Spring, Arizona (collected by Dr. Rothrock in 
1874), and from the Mexican Boundary Line south of Bisbee 
(collected by Dr. Mearns in 1892), and from some of the localities 
previously mentioned. There are also specimens labeled ‘‘Ari- 
zona’’ and one labeled Mexico. 
Localities where Thurberia has been found in Arizona have 
been indicated on maps and colored belts drawn to show where 
it has been, or is likely to be, found at irregular intervals. These 
belts represent sections of the upper division of Lower Sonoran 
zone but are carried out only where it occurs on mountain slopes 
with south, west or east exposures. The plant has not been 
found, so far as I am aware, on the northern, or cold, slopes of 
mountains nor in open valleys or plains country. 
THE PLANT 
The plant is a shrub, usually four to ten feet in height, with 
a woody stem often two inches in diameter. It has an open, 
spreading top, deeply cut three-lobed leaves, large pink flowers 
and small naked capsules, which resemble little cotton bolls 
without enveloping squares. The capsules are full of naked 
black seeds and a little fuzzy cotton fiber clinging to the inner 
walls. The plant blossoms late in summer and on October 19) 
in Sabino Canyon of the Santa Catalina Mountains, the flowers 
were gone. The bolls were practically all full grown with ripe 
