Small Leaved Horsebean 



543 



brown bark is about 3 mm. thick, smooth or somewhat scaly. The twigs are zig- 

 zag, short-hairy when young, smooth when older, yellowish green, and bear spines 

 2 cm. long or less. The leaves are obscurely bipin- 

 nate; the pinnae, springing from a very short enlarged 

 spinescent stalk, are 2 to 4 dm. long, with a very flat 

 rachis 2 to 3 mm, wide, supporting 25 to 30 pairs of 

 distant leaflets, which are linear-oblong to obovate, 

 1.5 to 8 mm. long, on very short slender stalks. The 

 flowers are fragrant, light yellow, and often appear 

 throughout the year in upright few-flowered racemes 

 7 to 15 cm. long; calyx-tube smooth, shorter than the 

 oblong reflexed lobes; petals spreading, nearly orbicu- 

 lar, 1.5 cm. long, the upper one red spotted; stamens 

 about half as long as the petals. The fruit is pendent, 

 clustered, cylindric, 5 to 10 cm. long, rather narrow, 

 long-tapering at each end, the calyx persistent at 

 the base; it is dark yellow to brown, with a few soft 

 hairs when young, becoming smooth; the seeds are far apart, oblong cylindric, 10 

 mm. long, 3 mm. in diameter. 



The wood is hard, very close-grained, Hght brown with thick yellowish sap wood ; 

 its specific gravity is about 0.61. It is frequently cultivated for ornament and 

 hedges and the foliage often used as fodder for goats and other domestic animals. 



Fig. 501. Horsebean. 



2. SMALL LEAVED HORSEBEAN Parkinsonia microphylla Torrey 



A small, much branched spiny tree or 

 shrub of rather rare occurrence in the deserts 

 of southern Arizona, southern Cahfomia, So- 

 nora, and Lower California, sometimes reach- 

 ing the height of 7.5 meters, with a tmnk 

 diameter of 3 dm. 



The bark is up to 6 mm. thick, usually 

 smooth or nearly so, dark yellow. The twigs 

 are stout and hair)', yellowish green, soon be- 

 coming smooth, and terminated by stift" spine- 

 hke tips. The leaves are early deciduous, 

 mostly falling away soon after unfolding; the 

 pinnae are 2.5 to 3 cm, long, the stalks slightly 

 winged and grooved ; the leaflets, 4 to 6 pairs, 

 are rather distant, ovate to oblong or nearly 

 round, 2 to 4 mm. long, blunt at each end, 

 sessile, densely hairy when unfolding, less so 

 Fig. 502. Small Leaved Horsebean. when okl. The flowers are pale yellow, ap- 



