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



1. FAGONIA 



Plant suffrutescent, puberulent to nearly glabrous; leaves digitately 

 3-foliolate, the stipules spinescent; flowers small, solitary in the leaf 

 axils; petals purplish pink; fruit of 5 united carpels. 



1. Fagonia californica Benth., Bot. Voy. Sulph. 10. 1844. 



Fagonia laevis Standi., Biol. Soc. Wash. Proc. 24: 249. 1911. 

 Fagonia longipes Standi., ibid. p. 250. 



Western Pinal County and Yuma County, 2,000 feet or lower, fre- 

 quent on dry rocky slopes and mesas, March and sometimes October. 

 Southern Utah to southern California, Sonora, and Baja California. 



F. laevis (type from Yuma, Jones in 1906) is a very nearly glabrous 

 form. F. longipes (type from Arizona without definite locality, 

 Palmer in 1876) has exceptionally long pedicels. 



2. LARREA. Creosotebush 



Plant a much-branched shrub, up to 3.5 m. (11.5 feet) high; leaves 

 evergreen, thick, glutinous, strong-scented, the leaflets 2, oblong to 

 obovate, united at base; flowers axillary, solitary; petals yellow; capsule 

 5-celled, densely white-villous. 



1. Larrea tridentata (DC.) Coville, Contrib. U. S. Natl. Herbarium 

 4: 75. 1893. 



Zygophyllum tridentatum DC, Prodr. 1: 706. 1824. 



Larrea glutinosa Engelm. in Wisliz., Mem. North. Mex. 93. 



1848. 

 Covillea tridentata Vail, Torrey Bot. Club Bui. 26: 302. 1899. 

 Covillea glutinosa Rydb., North Amer. Fl. 25: 108. 1910. 



Mohave County to Greenlee, Cochise, Santa Cruz, Pima, and Yuma 

 Counties, 5,000 feet or lower, dry plains and mesas, flowering from 

 time to time throughout the year but most profusely in spring. 

 Western Texas to southern Utah, Arizona, California, and northern 

 Mexico. 



Very closely related to L. divaricata Cav. of southern South America 

 and perhaps not specifically distinct, in which case the name divaricata 

 has priority. Often erroneously called "greasewood" in Arizona and 

 California. An outstanding xerophyte and a very important element 

 of the perennial desert flora in southern and western Arizona. The 

 plants cover thousands of square miles in the western and southwestern 

 parts of the State, often in nearly pure stand, usually with remarkably 

 little variation in size. The Pima Indians formerly used the leaves 

 in decoction as an emetic and to poultice sores. Small quantities of 

 lac are found on the branches as a resinous incrustation. This was 

 used for fixing arrow points, mending pottery, etc. Creosotebush has 

 a strong characteristic odor, especially noticeable when the foliage is 

 wet. The plant ordinarily is not touched by livestock although it is 

 reported that sheep, especially pregnant ewes, have been killed by 

 partaking of it. This plant is reported to cause dermatitis in 

 exceptional persons who are allergic to it. 



3. TRIBULUS. Caltrop 



Plant annual, with long prostrate stems radiating from the root; 

 leaves pinnate, the leaflets 8 to 12; flowers small, axillary, solitary, 



