562 TREES OF NORTH AMERICA 



buds. Bark dark orange color, generally smooth, although sometimes roughened 

 by scattered clusters of short pale gray horizontal ridges, becoming on old trees \' 

 thick. 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. 



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

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

 the neighborhood of Wickenburg, Arizona. 



10. CERCIDIUM, Tulasne. 



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

 armed with slender straight axillary spines. Leaves alternate, abruptly pinnate, 

 petiolate, early deciduous; pinnae 2 or occasionally 3, 7-8-f oliolate ; stipules incon- 

 spicuous or 0; leaflets ovate or obovate, without stipels. Flowers 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 revolute; petals orbicular or oblong, unguiculate, bright 

 yellow, the upper one broader and longer clawed than the others, slightly auriculate 

 at the base of the blade, the claw conspicuously glandular at the base ; stamens 10, 

 inserted with the petals on the margin of the disk, free, slightly decimate, exserted; 

 filaments filiform, pilose below, the upper one enlarged at the base and gibbous on 

 the upper side; anthers uniform, ovate, versatile; ovary short-stalked, inserted at the 

 base of the calyx-tube; styles slender, involute, infolded in the bud, with minute 

 terminal stigmas; ovules suspended from the angle of the ovary opposite the pos- 

 terior petal. Legume linear-oblong, compressed or somewhat turgid, straight or 

 slightly contracted between the seeds, thickened on the margins, the ventral suture 

 acute, or slightly grooved, tipped with the remnants of the style, tardily dehiscent, 

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

 pended longitudinally on long slender funicles, ovate, 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 dis- 

 tributed 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 territory of the United States two are small trees. 



Cercidium produces hard wood sometimes used as fuel. 



The generic name, from KepttlSiov, refers to the fancied resemblance of the legume 

 to the weaver's instrument of that name. 



CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT SPECIES. 



Legume compressed, with straight margins ; leaflets green, slightly glandular. 



1. C. floridum (E). 



Legume somewhat turgid, the margins often slightly contracted between the seeds ; leaf- 

 lets glaucous. 2. C. Torreyanum (G, H). 



1. Cercidium floridum, Benth. Green-barked Acacia. 



Leaves I'-l^' long, with 2 or rarely 3 pinnae, broad pubescent petioles and rachises, 

 and oval or somewhat obovate dull green puberulous minutely glandular leaflets 



