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 less 

 easily solved. 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 acquainted with its peculiar 

 possibilities. The mesquite (Prosopis glandulosa, pi. 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 valleys. 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 tornLUo (Strombocarpa pubes- 

 cens y pi. 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 wislizeni) accompanied by a thick undergrowth of small 

 shrubs. The cottonwood, which often reaches a large size, is used 



