32 LEGUMINOS^. Prosopis. 



reaching its greatest development, within the United States, in the valley 

 of the Santa Cruz and other streams of southern Arizona ; in western 

 Texas, owing to the annual burning of the prairies, rarely 1 metre in 

 height, the roots then enormously developed, often weighing several 

 hundred pounds, and forming, as they are here locally known, " under- 

 ground forests," furnishing the best and cheapest fuel of the region. 



Wood heavy, very hard, not strong, close-grained, compact, difficult to 

 work, almost indestructible in contact with the soil, containing many 

 evenly distributed, rather large, open ducts ; medullary rays numerous, 

 distinct ; color rich dark brown or often red, the sap-wood clear yellow ; 

 exclusively used for the beams and underpinnings of the adobe houses of 

 New Mexico, Arizona, and northern Mexico, for posts and fencing, and 

 occasionally in the manufacture of furniture, the fellies of heavy wheels, 

 etc. ; the best and often the only fuel of the region, burning slowly with 

 a clear flame, and producing valuable charcoal, but unsuited for the gen- 

 eration of steam on account of its destructive action upon boilers. 



A gum resembling gum-arabic is yielded by this species ; the unripe 

 and pulpy pods rich in grape sugar, are edible, furnishing valuable and 

 important fodder. 



94. Prosopis pubescens, Benth. 



Screw Bean. Screw-pod Mesquit. Tornilla. 



Valley of the Rio Grande in western Texas, west through Xew Mex- 

 ico and Arizona to southern California, southern Utah and southern Ne- 

 vada ; in northern Mexico. 



A small tree, rarely 9 metres in height, with a trunk sometimes 0.30 

 to 0.45 metre in diameter, or often a tall, much-branched shrub; sandy 

 or gravelly river-bottoms, reaching its greatest development, within the 

 United States, in the valleys of the lower Colorado and Gila Rivers. 



Wood heavy, exceedingly hard, not strong, brittle, close-grained, com- 

 pact, containing many evenly distributed open ducts; medullary rays 

 numerous, thin; color light brown, the sap-wood somewhat lighter; 

 used for fuel and fencing. 



The pods used as fodder are sometimes made into flour by the Indians. 



95. Leucsena glauca, Benth. 



Western Texas, — San Saba to Devil's River ; in northern Mexico ; 

 semi-tropical Florida (introduced) ; and through the West Indies. 



A small tree, 7 to !> metres in height, with a trunk 0.10 to 0.15 metro 

 in diameter ; or often a tall or, in Florida, low shrub, sending up many 

 stems from the ground. 



Wood heavy, hard, close-grained, compact, containing many small 

 regularly distributed open ducts ; layers of annual growth ami medullary 

 ravs hardly distinguishable; color rich brown streaked with red, the sap- 

 wood clear yellow. 



