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



is finer and more appressed than in var. subvelutina, and the petioles are 

 usually glandular-hispid in the latter variety, not so in var. luxurians. 

 But there is so much intergradation among all forms of this species 

 that the attempt to maintain even varieties is scarcely worth while. 



32. OLNEYA. Tesota 



A tree, attaining a height of 9 m. (27 feet) and a trunk diameter of 

 45 cm. (1.5 feet), the branches armed with spines, the bark thin and 

 scaly; leaves pinnate, the leaflets 8 to 24 (commonly 11 to 15), grayish 

 pubescent; flowers pealike, in short racemes; corolla about 12 mm. 

 long, purple and white; pods glandular-pubescent, usually several- 

 seeded and torulose. 



Known commonly in Arizona as ironwood, or palo-de-hierro. A 

 desert tree with very handsome flowers, limited to warm locations, 

 and for this reason used as an indicator in selecting sites for citrus 

 orchards. The foliage is evergreen except in very cold winters. The 

 wood is brittle, hard, remarkably heavy, and burns very slowly, 

 making good coals. The ironwood has been used so extensively for 

 firewood that it is unusual to find a large tree that has not been cut 

 back to the stump. The wood was used by the Indians for arrow- 

 heads and for tool handles. Experiments have been made to utilize 

 it commercially, but it is too hard for ordinary woodworking tools. 

 The hard sharp spines of the branches do not prevent desert-bred 

 horses from eating the foliage with evident relish. The seeds are an 

 important food of desert animals and formerly were eaten parched by 

 the Pima Indians (pi. 15). 



1. Olneya tesota A. Gray, Amer. Acad. Arts and Sci. Mem. ser. 2, 5: 



328. 1855. 

 Maricopa, Pinal, Pima, and Yuma Counties, 2,500 feet or lower, 

 common along washes in the foothills, May and June. (A collection 

 by B. E. Fernow, labeled " Pinery Creek" (Cochise County), must 

 have come from an altitude of 4,000 feet or more, if correctly labeled 

 as to locality.) The type was collected along the Gila River, Arizona. 

 Southern Arizona, southeastern California, Sonora, and Baja Cali- 

 fornia. 



33. DIPHYSA 



Plant a low shrub; branches of the inflorescence armed with short 

 weak prickles; leaves pinnate, the leaflets numerous, thin, oval to 

 suborbicular, 1 to 1 .5 cm. long; flowers rather large, in axillary racemes; 

 corolla yellow or yellowish; pods 1-celled, the outer wall separating 

 from the inner wall, forming 2 elongate bladderlike cavities paralleling 

 the seed cavity. 



1. Diphysa thurberi (A. Gray) Rydb. ex Standi., Contrib. U. S. Natl. 

 Herbarium 23: 479. 1922. 



Daubentonia thurberi A. Gray, Amer. Acad. Arts and Sci. 

 Mem. ser. 2, 5: 313. 1855. 



Montezuma Camp, southeast of the Huachuca Mountains (Lemmon 

 2659), the only record for Arizona. Southeastern Arizona and north- 

 ern Mexico. 



