162 LEGUHINOS^E. Parkinsonia. 



obliquely or longitudinally veined, thin-coriaceous, usually more or less torulose and 

 compressed between the seeds. Seeds compressed, broadly oblong, longitudinal, 

 albuminous ; hilum minute. Trees or shrubs, often armed with short spines : 

 leaves bipinnate with 1 or 2 pairs of pinnas ; the common petiole short, often obso- 

 lete or spinescent ; stipules minute or none ; flowers yellow or whitish, on slender 

 pedicels in short loose axillary or terminal racemes. Cercidium, Tulasne. 



A genus of 8 species, one of S. Africa, three of S. America" (including P. aculeata which is 

 widely distributed through tropical America), the remainder belonging to the region between Texas 

 and S. California. 



* Leaflets usually very numerous, upon a much-elongated flattened rhachis : divis- 

 ions of the calyx narrowly imbricate in the bud. 



1 . P. aculeata, Linn. A small tree, glabrous throughout, the slender branches 

 often pendulous : spiny petioles a half to an inch long or less, bearing 1 or 2 pairs of 

 pinna? near the base, or wanting ; leaflets very small, oblong, scattered upon a broad 

 rhachis ^ to 1| feet long; stipules small, spinescent : racemes axillary 3 to 6 inches 

 long : pedicels jointed a little below the flower : stamens shorter than the yellow 

 petals : pod 2 to 10 inches long, 1 -5-seeded, attenuate at each end and contracted 

 between the distant seeds. Benth. in Mart. Fl. Bras. xv 2 . 78, t. 26. 



Hills of the Colorado near Fort Yuma, and through Mexico to Texas. Probably of American 

 origin, but now naturalized or cultivated in most of the tropical and warmer regions of the globe. 



* * Pinnae short and leaflets few ; rhachis terete: calyx valvate in the bud. 



2. P. microphylla, Torr. A much-branched shrub, 5 to 10 feet high, with 

 smooth light-green bark, the straight rigid branchlets spinose at the ends ; younger 

 branches and inflorescence somewhat pubertilent : common petioles very short or 

 none, not spinescent or rarely so ; leaflets 4 to 6 pairs in each pinna, broadly oblong 

 or nearly orbicular, obtuse or acutish, not narrower at the oblique base, two lines 

 long or less, glaucous : racemes short (an inch long or less), axillary and sessile ; 

 pedicels evidently jointed a little below the flower : petals deep straw-color, the 

 upper one white, 3 or 4 lines long : anthers orange, exserted : ovary appressed- 

 silky : pod attenuate at each end, 1 - 3-seeded, contracted between the seeds, 2 or 3 

 inches long. Bot. Mex. Bound. 59 ; Benth. 1. c. 



On the Colorado near Fort Yuma, on Bill Williams River, and eastward through S. Arizona ; 

 flowering in May. 



3. P. Torreyana, Watson. A small tree, 20 or 30 feet high, with light green 

 and smooth bark ; younger branches and leaves sparingly pubescent : leaflets 2 or 3 

 pairs, oblong, obtuse, narrower toward the scarcely oblique base, 2 or 3 lines long, 

 glaucous : flowers on longer pedicels in racemes terminating the branches : pedicels 

 jointed near the middle, the joint not evident until in fruit : petals 4 lines long, 

 apparently bright yellow ; gland upon the upper petal very prominent : ovary gla- 

 brous : pod 2 or 3 inches long, with a double groove along the broad ventral suture, 

 acute, 2 - 8-seeded, scarcely or decidedly contracted between the very thick seeds. 



Proc. Am. Acad. xi. 135. Cercidium floridum, Torrey, Pacif. R. Tiep. v. 360, 

 t. 3 ; not of Benth. 



A frequent tree in the Valley of the Colorado and eastward ; the Palo Verde of the Mexicans, 



usually bare of foliage, the leaves being soon deciduous. The species has been mistaken for 

 the P. jtorida (Cercidium floridum., Benth.) of the Rio Grande Valley, which has axillary 

 racemes, pods with a narrow acute margin on the ventral side, thinner seeds, and somewhat larger 

 leaflets. 



20. PROSOPIS, Linn. MESQUIT. SCREW-BEAN. 



Flowers regular. Calyx campanulate ; the teeth very short, valvate. Petals 5, 

 valvate, united below the middle or at length free, woolly on the inner side (in our 



