28 BOTANICAL FEATURES OF NORTH AMERICAN DESERTS. 
More than one of the species in both groups assume an arboreal form, 
while several were encountered which were definitely known to be as yet 
undescribed. 
A great number of woody shrubs of the type known in such arid 
regions were seen on the hill-slopes, while down near the streamways an 
ash (fraxinus) assumed well-developed proportions. The plant most 
reminiscent of the tropics, however, is the Fzcus, which in favorable 
situations shows a great spread of branches and makes a large number 
of roots above the surface of the ground. 
In the markets of the villages from Oaxaca to Mitla trimmed root- 
stocks of a yucca were on sale which are used by the native population 
for soap, especially in dressing the hair, although it probably is applied 
otherwise also. 
At Mitla were seen a few living specimens of Nopalea, a cactus not 
encountered elsewhere on the trip, while a similarly rare form, Peres- 
kiopsis chapistle, was seen in the suburbs of Oaxaca. The latter was 
in close proximity to a huge shrub, probably a Boehmeria, or some other 
member of the nettle family, which was sedulously avoided by our driver 
as being capable of inflicting very painful stings. 
At Mitla the opportunity was offered for seeing the manufacture of 
mescal from Agave. Plants of several species and horticultural varieties 
of Agave, as well as of Yucca and Dasylirton, are uprooted at a time when 
the plant is about to send up its long inflorescence axis and is loaded with 
sugary substances. The leaves and roots are trimmed away, leaving a 
huge core in the case of the large agaves. A large pit is heated by means 
of a hardwood fire built in it, and after being cleansed of ashes and the 
remains of the fire the cores are piled in the cavity and covered, and 
allowed to bake slowly for two or three days. Next the pit is uncovered 
and the cores removed to a large vat made by sewing the edges of three 
or four cowskins together and suspending them from a framework of 
rough branches. Fermentation is allowed to act upon the sugary material 
for a week or ten days, and then the unpleasantly smelling liquid is 
dipped out and put in the kettle of a rudestill, the cap of which is con- 
nected with pipes cooled with water run in wooden conduits from a stream 
or acequia near by. The resulting liquor contains a mixture of several 
alcohols and is exceedingly fiery, being a true whisky of a desert people. 
SAGE-BRUSH DESERTS OF NEVADA AND UTAH. 
A large area in Nevada and Utah, lying at elevations up to 5,000 feet, 
includes numerous valleys and widely extended plains with no outlet 
for the drainage. Into these the streams from the mountains flow and 
terminate in lakes at the lowermost part of the natural basin formed, 
or spread out in great flats or playas in such manner that the waters dis- 
appear in the ground, forming what are known as sinks, of which that of 
