FOREST TREES OF THE PACIFIC SLOPE. 373 



Longevity. — Not fully determined. A tree 7 inches in diameter was i.'4 

 years old. 



Texas (lower Rio Grande i ; Arizona and California (in valley of Colorado ttiver) ; 

 northern Mexico and Lower California. 



OCCURRENCE. 



About lagoons (Colorado River Valley) ; in rich, wet silt or mud. Scattered singly 

 or in groups. 



Climatic Conditions. — Similar to those of mesquites. Nothing is known of its 

 tolerance and reproduction. 



Little-leaf Horse-bean. 

 Parkmsonia mdcrophylla Torrey. 



DISTINGUISHING CHARACTERISTICS. 



So far as can be discovered, this tree, which is generally shrubby, has no 

 field name, prohably because it is not recognized by laymen as a relative of the 

 preceding species. For want of a better one, "little-leaf horse-bean." coined 

 from the technical name, is proposed. 



At best 15 or 20 feet high, with a short trunk from 6 to 10 inches through; 

 very often only a shrub from 3 to G feet high, with numerous steins. The crown 

 is always intricately branched, and the limbs are armed with many short, stiff. 

 spine-pointed twigs. Bark of branches and trunk smooth and pale reddish yel- 

 low ; the greenish twigs are densely covered at first with minute woolly hairs. 

 most of which disappear by autumn. The pale yellow flowers, borne in short. 

 delicate, branched clusters, appear before the leaves in late spring from minute 

 buds on thorny twigs formed the previous year (fig. 175) ; upper central divi- 

 sion of the flower, white. The minutely hairy loaves (fig. 175) appear in early 

 summer, but fall shortly after reaching maturity, so that the twigs, as ordinarily 

 seen in middle or late summer, are bare, save for clusters of striped pods (fig. 

 175), which commonly remain on the branches until the following spring. The 

 pods contain from 1 to .". i as a rule. 2) seeds. Wood, very dense, line-grained, 

 hard, deep yellowish brown, often mottled and streaked with dull red: a large 

 part of the stem is yellowish sapweod. Sizable trees are so rare as to render 

 the wood of no commercial or domestic use. 



Owing to its shrubby, leafless form and generally rare occurrence, it can 

 hardly prove of any importance to the forester, even though it thrives in the 

 hottest and most arid situations. 



Longevity. — Not fully determined. One tree 91 inches in diameter showed an 

 age of 50 years. 



Southern Arizona (desert region i : southern California (desert region adjoining Ari- 

 zona; Lower California (adjoining California); Mexico iSonora). 



