LEGUMINOS.E 613 



erally smooth, although sometimes roughened by scattered clusters of short pale gray 

 horizontal ridges, becoming on old trees f thick; more often a shrub, frequently only a 

 few feet tall. Wood heavy, hard, close-grained, dark orange-brown streaked with red, 

 with thick light brown or yellow sapwood of 25-30 layers of annual growth. 



Fig. 561 



Distribution. Deserts of southern Arizona and adjacent regions of California and 

 Sonora, and in northern Lower California; known to attain the size and habits of a tree 

 only in the neighborhood of Wickenburg, Maricopa County, Arizona. 



10. CERC1DIUM Tul. 



Trees or shrubs, with stout tortuous branches, covered with bright green bark and armed 

 with slender straight axillary spines, and minute obtuse buds. Leaves alternate, abruptly 

 pinnate, petiolate, early deciduous; pinnae 2 or occasionally 3, 6-8-foliolate; stipules incon- 

 spicuous or ; leaflets ovate or obovate, without stipels. Flowers perfect in short few-flowered 

 axillary racemes, solitary or fascicled, with minute membranaceous early deciduous bracts; 

 calyx 5-lobed, the lobes equal, acute, reflexed at maturity, their margins scarious, slightly 

 re volute; petals orbicular or short-oblong, unguiculate, bright yellow, the upper petal 

 broader and longer clawed than the others, slightly auriculate at base of the blade, the 

 claw conspicuously glandular at base; stamens 10, inserted with the petals on the margin 

 of the disk, free, slightly declinate, exserted; filaments filiform, pilose below, the upper 

 filament enlarged at base and gibbous on the upper side; anthers uniform, ovoid, versatile; 

 ovary short-stalked, inserted at the base of the calyx-tube; styles slender, involute, in- 

 folded in the bud, with a minute terminal stigma; ovules suspended from the angle of the 

 ovary opposite the posterior.petal. Legume linear-oblong, compressed or somewhat tur- 

 gid, straight or slightly contracted between the seeds, thickened on the margins, the ven- 

 tral suture acute, or slightly grooved, tipped with the remnants of the style, tardily de- 

 hiscent, 2-valved, the valves membranaceous or subcoriaceous, obliquely veined. Seeds 

 suspended longitudinally on a long slender funicle, ovoid, compressed, the minute hilum 

 near the apex; seed-coat thin, crustaceous; embryo compressed, light green, covered on 

 the sides only by a thin layer of horny albumen; cotyledons oval, flat, rather fleshy; radicle 

 very short, erect, near the hilum. 



Cercidium is confined to the warmer parts of the New World, where it is distributed 

 with four or five species from the southern borders of the United States through Mexico, 

 Central America, and Venezuela to Mendoza. Of the three species found within the ter- 

 ritory of the United States two are small trees. 



