590 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



2. Leaves short-petioled, ovate to lanceolate, commonly more than 6 mm. wide, 

 denticulate or dentate, somewhat shiny; inflorescences densely panicu- 

 late; floral bracts ovate or lanceolate, not cordate, often denticulate, 

 more or less acuminate, rough-pubescent; petals 7 to 10 mm. long (3). 

 3. Petals 7 to 8 mm. long; leaf blades ovate, few-dentate, usually coarsely so, 

 rounded, truncate, or short-cuneate at base; stems herbaceous above. 



3. P. NITIDUS. 



3. Petals about 10 mm. long, white, the claws strongly coherent; leaf blades 



lanceolate to ovate, finely crenate, cuneate at base; stems almost 



wholly woody 4. P. parryi. 



1. Petalonyx thurberi A. Gray, Amer. Acad. Arts and Sci. Mem. ser. 



2,5: 319. 1855. 

 Mohave, Maricopa, Pinal, Pima, and Yuma Counties, up to 

 5,000 feet but usually much lower, common in sandy soil, often in 

 dry stream beds, May to October, type from the Gila River valley 

 (Thurber). Arizona, Nevada, southeastern California, and north- 

 western Mexico. 



2. Petalonyx linearis Greene, Calif. Acad. Sci. Proc. 4: 188. 1885. 

 Yuma County near Laguna Dam on the Colorado River (Jones in 



1906, Harrison and Peebles 5060) and at Tinajas Altas (Goodding in 

 1938), March. Southwestern Arizona, southeastern California, and 

 Baja California. 



3. Petalonyx nitidus S. Wats., Amer. Nat. 7: 300. 1873. 



Yucca, Mohave County, 1,800 feet {Jones 4483), May. Western 

 Arizona, southern Utah and Nevada, and southeastern California. 



4. Petalonyx parryi A. Gray, Amer. Acad. Arts and Sci. Proc. 10: 72. 



1874. 



Northern Arizona (Palmer in 1877), Mokiak Pass, Mohave County, 

 3,000 feet (Cottam et al. 4410), northern Mohave County (Peebles 

 and Parker 14752), dry washes, etc., May. Southern Utah and 

 Nevada, and northern Arizona. 



A rounded shrub about 3 feet high. 



3. MENTZELIA.8 7 Blazing-star, stickleap 



Plants annual or perennial, herbaceous or suffrutescent ; herbage 

 scabrous, without stinging hairs; flowers in terminal cymose inflores- 

 cences, or some of them solitary in the forks of the branches, small or 

 large, cream-colored, yellow, or orange; stamens usually numerous, 

 the outer ones often petallike. 



As one of the common names implies, fragments of the leaves and 

 stems stick readily to clothing and to the hair of animals. Many of 

 the species are handsome in flower. 



Key to the species 



1. Outer filaments deft at the dilated apex, the anther borne on a slender pro- 

 longation of the filament between the 2 subulate or triangular-lanceolate 

 teeth or lobes; petals ochroleucous, 2 to 4 cm. long; flowers closely sub- 

 tended by deeply laciniate bracts; stems stout, white or whitish, seldom 

 more than 30 cm. long, branching at or near the base: Section Bicuspi- 

 daria (2). 



87 Reference: Darlington, Josephine, a monograph of the genus mentzelia. Mo, Bot. Gard. 

 Ann. 21: 103-226. 1934, 



