TREES AND SHRUBS 93 



The Mimosa or Acacia Family (Mimosaceae) contains 

 several shrubs of considerable importance that grow mainly 

 upon the lower, hotter, and drier mesas and in the foothills 

 of the mountains. Five genera are represented. These plants 

 may be recognized by their once or twice compound leaves 

 with numerous very small leaflets; their inconspicuous regular 

 flowers, usually clustered in circular heads or spikes and hav- 

 ing numerous stamens ; their spiny stems and bean-like fruits. 



Two species of Acacia (A. greggii and A. constricta) 

 are common shrubs on the mesas and in the arroyos. Acacia 

 greggii is sometimes called Cat Claw, while the other species 

 has no common name. The former is of some value as a 

 forage plant in the region where it grows, being browsed 

 more or less extensively by cattle. Its flowers are pale dirty 

 white and the pod is a flattened one, ^4 inch wide and several 

 inches long, more or less twisted and bent. Acacia constricta 

 forms large patches of shrubs 3 to 5 feet high on the driest of 

 our gravelly mesas. Its flowers are bright yellow in spherical 

 heads about Y\ inch in diameter, and very pleasantly per- 

 fumed. The fruit is a straight cylindrical pod 3 to 4 inches 

 long, % inch in diameter, and constricted between the seeds. 

 This little plant is worth cultivating, though we have been 

 but partially successful in transplanting it. 



The Tornillo or Screw Bean (Strombocarpa pubescens) 

 is one of the common large shrubs of the river valleys in the 

 southern part of the State, where it is everywhere known 

 under its Spanish name. It is economically of great import- 

 ance, since the larger stems or trunks are used for fence posts 

 and serve very well for this purpose, since they do not decay 

 rapidly. The wood is extensively used for fuel, being the best 

 for this purpose to be had at the lower levels. Under cultiva- 

 tion the plant grows with fair rapidity and produces a char- 

 acteristic slender and graceful shrub which will work in well 

 for mass planting in situations where the temperature is high 

 and the water supply small. 



