Psorothamnus spinosus (A. Gray) Barneby

Psorodendron spinosum (A. Gray) Rydberg
Dalea spinosa A. Gray, Mem. Am. Acad. II. 5: 315. 1S54. Asagraea spinosa Baillon, Adansonia 9: 233. 1870. Dalea spinescens Hemsl. Biol. Centr. Am. Bot. 1: 247. 1S80. Parosela spinosa A. Heller, Cat. N. Am. PI. ed. 2. 7. 1900.
An intricately branched spinescent tree or shrub, 4—7 m. high; branches at first minutely canescent, later becoming glabrous, yellowish-green, conspicuously glandular-dotted, the glands at first conic; leaves simple, white-strigose, those of the young plant obovate, spatula te or oblanceolate, irregularly dentate, 2-5 cm. long, those of the branches linear-oblanceolate, 5-15 mm. long, early deciduous; racemes 3-5 cm. long, spinescent; bracts and bractlets minute, subulate; pedicels 1 mm. long or less; calyx densely white-strigose; tube turbinate, sharply 10-ribbed, with a solitary conspicuous gland in each interval, 3 mm. long; lobes ovate, acute, 1.5 mm. long; corolla dark-blue; blade of the banner broadly obcordate, 4 mm. long, those of the wings obliquely oval, with a conspicuous basal lobe, 4-5 mm. long, those of the keel-petals broader and with a more rounded basal lobe, about 6 mm. long, the claws of the wings and keelpetals about 2 mm. long; pod obliquely ovate, canescent and glandular-dotted.
Type locality: Arroyos of the Gila, Arizona.
Distribution: Southern California, Arizona. Sonora. and Lower California.

Perennial, Trees, Shrubs, Woody throughout, Stems woody below, or from woody crown or caudex, Nodules present, Stems erect or ascending, Stems or branches arching, spreading or decumbent, Stems less than 1 m tall, Stems 1-2 m tall, Stems greater than 2 m tall, Trunk or stems armed with thorns, spines or prickles, Plants gland-dotted or with gland-tipped hairs, Stems solid, Stems or young twigs sparsely to densely hairy, Stems silvery, canescent, tomentose, cobwebby, or wooly, Leaves alternate, Leaves petiolate, Stipules inconspicuous, absent, or caducous, Stipules setiform, subulate or acicular, Stipules deciduous, Stipules free, Leaves simple, or appearing so, Leaf or leaflet margins entire, Leaflets alternate or subopposite, Leaflets 1, Leaves glandular punctate or gland-dotted, Leaves glabrous or nearly so, Inflorescences racemes, Inflorescences spikes or spike-like, Inflorescence axillary, Inflorescence or flowers lax, declined or pendulous, Bracts very small, absent or caducous, Flowers zygomorphic, Calyx 5-lobed, Calyx gland-dotted or with glandular spot, Calyx hairy, Petals separate, Corolla papilionaceous, Petals blue, lavander to purple, or violet, Banner petal suborbicular, broadly rounded, Wing petals narrow, oblanceola te to oblong, Wing tips obtuse or rounded, Keel tips obtuse or rounded, not beaked, Stamens 9-10, Stamens monadelphous, united below, Filaments glabrous, Style terete, Fruit a legume, Fruit unilocular, Fruit indehiscent, Fruit oblong or ellipsoidal, Fruit exserted from calyx, Fruit glabrous or glabrate, Fruit gland-dotted or with gland-tipped hairs, Fruit 1-seeded, Fruit 2-seeded, Seeds ovoid to rounded in outline, Seed surface smooth, Seeds olive, brown, or black.