172 



ground forests — and fnrnislies a cheap and valuable fuel. The tim- 

 ber is heav}^, very hard, and possesses remarkable durability. It is 

 employed chiefly for fuel, tie-timber, and fenciugv but somewhat for 

 heavy wheel stock and in the manufacture of cluircoal. 



Description. — Leaves compound, twice pinnate, single or in clusters, with a pair of 

 stiff, straight, yellowish thorns i to ^ inch long at the base of each leafstalk or 

 cluster; leaflets J to If inches long, by to i of an inch wide, elliptic-oblong to lance- 

 linear. A cup-shaped gland at the end of the main leaf-stem, (where the usually 

 single pair of smaller stems (pinufe) with leaflets is given off). Pods somewliat flat- 

 tened, straightish or curved, 3 to 7^ inches long, i to | an inch wide ; composed of 12 

 to 25 lobe-like joints (containing as many seeds), and terminating in an awl-point ; 

 young pods covered with a dense velvety down, yellowish-white when mature. They 

 have a sweet taste, and are often used for fodder. 



40. — Screw Bean. Screw-pod. Mesquit. Tornilla. {Prosopis 



piihescens^ Benth.) 



A small tree or shrub growing on gravelly or sandy bottom-land, 

 through New Mexico (in western Texas, through Arizona to California; 

 southward into Mexico); said to attain its largest size within the 

 United States in the valleys of the lower Colorado and Gila Eivers— 

 20 to 25 feet in height, and C to 12 inches in diameter. The wood is 

 heavy, very hard, and brittle, but exceedingly durable, and is used for 

 fencing and fuel. Pods sweet, sometimes used for fodder, and for flour 

 by Indians. 



Description. — Leaves essentially as in Prosopis juliflora (No. 39), with a pair of 

 straight pearly-white thorns at base of each leaf or cluster; leaflets elliptic-oblong, 

 often with a short fine point (x)robably less variable in size than those of the preced- 

 ing species), i to i an inch long, and -^^ to ^ of an inch wide. Pods cylindrical, 1 

 to 2| inches long, -J- to i of an inch in diameter, straightish or crooked, closely coiled 

 in a spiral ; clothed with a fine velvety down ; light brown at maturity. Brauchlets 

 with white longitudinal (decurrent) lines proceeding from the bases of the thorns. 



41. — Cat's Claw. [Acacia Greggii, Gray.) 



Often a shrub, or a low much-branched tree, 20 to 25 feet in height and 

 sometimes 10 inches in diameter, growing abundantly on the dry table- 

 lands and in the low canyons of southern Utah (Dr. Palmer), New Mex- 

 ico and Arizona (extending to California; also in northern Mexico and 

 western Texas). The wood is heavy, very hard and strong, furnishing 

 good fuel. Large trees often hollow. 



Description. — Leaf-stems short, giving off 2 to :i pairs of smaller stems (pinnaj) which 

 bear 3 to 6 pairs of very small (i to ^- of an inch long) oblong-ovate (broader above) 

 unequal-sided leaflets, with a rounded or abrupt apex, downy. Pods smooth, flat, 

 curved, 3 to 6 inches long, and ^ to f of an inch broad ; usually with constrictions 

 between the seeds; the latter flat, obicular, and dark brown. Branches sparingly 

 armed with short hooked prickles, or occasionally unarmed, sometimes with whitish 

 lines. 



