USEFUL NATIVE PLANTS OF NEW MEXICO—STANDLEY. 461 
In the river valleys, often far removed from forested mountains, 
or separated by almost impassable country, the fuel question is iss 
easily sale There is a widely quoted saying that in the South- 
west men ‘‘dig for wood and climb for water.” The first part of this 
statement is literally true. The people of southern and southwestern 
New Mexico, like those of the adjacent regions, depend for fuel 
largely, if not chiefly, upon a low, straggling, spiny shrub, which 
would certainly be ignored by one not beqanintod with its peculiar 
possibilities. The mesquite (Prosopis glandulosa, pl. 13) is a widely 
distributed and characteristic plant of all the Southwest, being in 
New Mexico always a low shrub, never more than 3 to 5 feet high, 
its slender branches seeming even more tenuous by reason of the 
sparse dissected foliage with which they are invested. The branches 
are so small that even were they all compressed into a solid block of 
wood they would still supply but scant fuel. The shrub’s value lies 
not in its branches and trunk, however, but in its roots. When the 
sand heaped about the stems is pushed away and the roots uncov- 
ered it becomes evident that the mesquite can be a source of a large 
amount of firewood. The roots have been developed more than is 
- common in woody plants, presumably that they may serve as stor- 
age organs for water, and thus enable the shrubs to exist in the arid 
regions where they grow. Many of the native Mexicans earn no 
inconsiderable part of their livelihood by digging mesquite roots 
upon the mesas or in the waste land of the cates: Each bush yields 
a large amount of wood, but there are no data available from which 
to determine the amount per acre. While in the form of very thick 
and gnarled hard roots, extremely difficult to cut or split, when 
finally prepared for the stove or grate the wood is of unexcelled 
quality. It can be burned green, but is improved by drying. The 
tops or branches are usually thrown away. Unimproved land in 
the valleys is generally covered with mesquite and removal of the 
bushes and roots must precede cultivation. 
A near relative of this shrub is the tornillo (Strombocarpa pubes- 
cens, pl. 4, A) or screw bean, which receives its English name—the 
exact equivalent of its Spanish one—from the shape of its pods, 
which are coiled into a long cylinder so as to resemble a screw. In 
the case of the tornillo the stems, not the roots, furnish fuel. These 
are little larger than an ordinary broomstick and would appear to 
be an unsatisfactory source of heat, but thousands of loads of them 
are cut in the valleys every year. The bushes grow only in the allu- 
vial lands. When cut off near the ground, they sprout up and are 
soon ready for cutting again. 
The land immediately bordering the principal streams is nearly 
always covered with bosques or groves of the valley cottonwood 
(Populus wislizent) accompanied by a thick undergrowth of small 
shrubs. The cottonwood, which often reaches a large size, is used 
