550 



TREES OF NORTH AMERICA 



Prosopis juliflora, var. velutina, Sarg. 



Leaves 5'-6' long, often fascicled, cinereo-pubescent, with short petioles and 12- 

 22 pairs of oblong or linear-oblong obtuse or acute crowded pale green leaflets \'-%' 

 long. Flowers in densely-flowered spikes 2'-3' long; calyx villose. 



A tree, often 50 high, with a trunk 2 in diameter, covered with rough dark 

 brown bark, and heavy irregularly arranged usually crooked branches. 

 Distribution. Hot valleys of southern Arizona and Sonora. . 



and 



2. Prosopis pubescens, Benth. Screw Bean. Screw Pod Mesquite. 



Leaves canescently pubescent, 2'-3' long, with slender petioles '-' in length, 

 pinuse l^'-2' long and 10-16-f oliolate ; stipules spinescent, deciduous; leaflets 



oblong or somewhat falcate, acute, sessile or short-petiolulate, often apiculate, con- 

 spicuously reticulate-veined, '-f' long, ^' wide. Flowers beginning to open in 

 early spring, and produced in successive crops from the axils of minute scarious 

 bracts, in dense or interrupted cylindrical spikes 2'-3' long ; calyx obscurely 5-lobed, 

 pubescent on the outer surface, one third to one fourth as long as the narrow 

 acute petals coated on the inner surface near the apex with thick white tomentum, 



