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.