Acacia. LEG-UMINOS^E. 163 



species). Stamens 10, free, exserted; anthers tipped with a deciduous gland. 

 Ovary villous (in American species) : style filiform. Pod linear, compressed or 

 nearly terete, straight, falcate, or twisted, coriaceous and indehiscent, usually becom- 

 ing thick and spongy within, and with thick partitions between the seeds. Seeds 

 numerous, ovate, compressed. Trees or shrubs, often armed with axillary spines 

 or spinescent stipules ; leaves bipinnate, with 1 or 2 pairs of pinnas, and usually 

 numerous small entire leaflets ; flowers small, greenish, in cylindrical or globose 

 axillary pedunculate spikes. 



Species about 18, of which 5 belong to Africa and tropical Asia, the remainder to Mexico and 

 South America, the following extending into the United States. 



% Pod elongated, straight or falcate, compressed or at length thickened and fleshy : 

 seeds each in a distinct cartilaginous envelope: spines axillary: spikes cylindrical. 

 ALGAROBIA, Beuth. 



1. P. juliflora, DC. A shrub or tree (sometimes 30 to 40 feet high), glabrous 

 or puberulent, with stout axillary spines or often unarmed : leaflets 6 to 30 pairs, 

 short-oblong to linear, 3 to 18 lines long, obtuse or acute : spikes shortly peduncled, 

 2 to 4 inches long, usually dense, 1 - 3-fruited : flowers nearly sessile, a line long : 

 pod 4 to 6 inches long or more, straight or curved, at first flat and constricted 

 between the seeds, 3 to 6 lines broad, at length sweet and pulpy within, acuminate, 

 longitudinally veiued ; stipe 3 to 6 lines long. Prodr. ii. 447 ; Benth. in Trans. 

 Linn. Soc. xxx. 377. P. glandulosa, Torrey, Ann. N. Y. Lye. ii. 192, t. 2. Alga- 

 robia glandulosa, Torr. & Gray, Fl. i. 399 ; Gray, PI. Wright, i. 60. Prosopis 

 odorata, Torr. in Frem. Rep. 313, t. 1, excl. fruit. 



This is the Algaroba of the Mexicans, or Honey Mesquit, found as a small shrub in Southeast- 

 ern California from San Felipe Canon to Fort Mohave, and eastward to Texas. The species in 

 various forms extends southward through Mexico, and along the Andes to Chili, and to Buenos 

 Ayres. The abundant fruit is eaten by the Indians and often by whites, and is a valuable food 

 for horses. The shrub also furnishes a valuable gum, resembling Gum Arabic, which in Texas and 

 Mexico is collected in considerable quantity for export. 



* * Pod thick, spirally twisted in numerous turns: stipules spinescent: sjnkes glo- 

 bose to cylindrical. STROMBOCARPA, Benth. 



2. P. pubescens, Benth. A shrub or small tree 15 to 30 feet high, resem- 

 bling the last, canescently puberulent or glabrate : leaflets 5 to 8 pairs, oblong, 3 to 

 4 lines long, acutish : spikes lax, 1^ to 2 inches long, on peduncles about equalling 

 the leaves, several-fruited: flowers sessile, 1| lines long: ovary very villous : pod 

 twisted into a narrow straight cylinder 1 or 2 inches long, pulpy within, nearly 

 sessile. Lond. Jour. Bot. v. 82, & 1. c. 380. Strombocarpus pubescens, Gray; 

 Torrey, Pacif. R. Rep. v. 360, t. 4. Prosopis Emoryi, Torrey, Emory Rep. 139. 



The Tornilla of the Mexicans, and Screw-bean or Screw-pod Mesquit of the Americans. In San 

 Diego Co. at Vallecito (Thurber), Mountain Springs (Palmer), Fort Mohave (Cooper), and east to 

 New Mexico. The pods are ground into meal and used for food by the Indians. P. cinerascens, 

 Gray, a species of the Rio Grande Valley with similar fruit, has much smaller leaves and leaflets, 

 the common petiole nearly obsolete, the slender spines usually exceeding the leaves, and the 

 flowers in long-peduncled globose heads. 



21. ACACIA, Willd. 



Flowers perfect or polygamous. Calyx 4 - 5-toothed. Petals more or less united 



below. Stamens numerous, exserted, free or united at base ; anthers small. Style 



filiform. Pod 2-valved or indehiscent, many-seeded, compressed and membrana- 



ceous or more or less thickened and rounded. Seeds compressed : albumen none. 



Shrubs or trees, often spinose or prickly ; leaves bipinnate, with small leaflets ; 



