Leguminosae. 



135 



Prosopis. Mesquite. 

 (Family Leguminosae). 



Shrubs or small trees. Twigs 

 moderate, zig-zag: pith minute, 

 angular, continuous. Buds mi- 

 nute, rather quickly developing 

 into stout spurs bristling with 

 stipules and frequently flanked 

 by a solitary spine or mostly a 

 pair of terete nearly straight 

 spines, the end-bud lacking. Leaf- 

 scars alternate, often 2-ranked, 

 somewhat raised, rounded or el- 

 liptical: bundle-traces 3: stipules 

 long persistent. Leaves of 2 pin- 

 nate leaflets terminating the pet- 

 iole) or of 4 such leaflets. (In- 

 cludes Strombocarpa) . 



Notwithstanding its compound 

 leaves, their characteristic droop- 

 ing position and the openly 

 branched top of the tree cause a 

 grove of mesquite to suggest a 

 peach orchard to many people when they see it for the first 

 time. As in many other Leguminosae the stipules of Prosopis 

 persist, even when they are not converted into spines; and 

 their presence gives a peculiar shaggy appearance to the axil- 

 lary spurs on which the foliage is clustered. 



The screw-bean or tornillo, P. pubescens, is separated 

 frequently from the other species under the generic name 

 Strombocarpa. 



1. Stipules becoming spines: downy. (1). P. pubescens. 

 Spines not representing the nodal stipules. 2. 



2. Glabrous. (Common mesquite). (2). P. glandulosa. 

 Leaves, and twigs above, gray-pubescent. P. velutina. 



