96 TREES AND SHRUBS 



or less, whitish; flowers yellow, in crowded spikes; pod an indehis- 

 cent spirally coiled legume. A typical plant of the Lower Sonoran 

 Zone. 



1. S. pubescent. 



3. PROSOPIS L. Mesquite 

 A much branched shrub 10 feet high or less, seldom larger, 

 with rigid, tough stems bearing large stipular spines; leaves bipin- 

 nate with 1 or 2 pairs of pinnae and numerous oblong entire leaflets; 

 flowers small, greenish yellow, in axillary spikes; fruit an indehiscent, 

 slightly compressed, straight or falcate legume. Mostly in the Lower 

 Sonoran Zone but reaching into the Upper Sonoran. 



1. P. glandulosa. 



4. ACUAN Medic. 

 Suffrutescent perennials with unarmed herbaceous stems and 

 bipinnate leaves with numerous small leaflets; flowers in axillary 

 pedunculate heads, greenish white: calyx sometimes pappiform or 

 wanting; stamens 5 or 10, the anthers not gland hearing; fruit a 

 flattened dehiscent legume, straight or acute. 

 A single species. 1. A. jamesii. 



5. MIMOSA L. Catclaw 

 Low shrubs with -terns armed with hooked opines; leaves 

 bipinnate, the leaflets small: flowers in spikes or heads, small; se- 

 pals and petals 5; stamens lo. distinct; fruit a flattened pod. armed 

 or unarmed, sometimes constricted between th< - 



Flowers in spikes (pink) 1. M. di/snrarpa. 



Flowers in spherical heads. 

 Pinnae 4 to 7 pairs, pubescent. 



Young stems not flexous, somewhat virgate: 

 pods usually not constricted between ire 

 seeds, straight. - M. lemmoni. 



Young stems flexous; pods more or less con- 

 stricted between the seeds, conspcu- 

 ously arcuate. 3. .1/. btuncifera. 



Pinnae 1 to 3 pairs, glabrous. 

 Pods more or less spiny. 4. .1/. borealis. 



Pods not spiny. If. fragrans. 



