540 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



Doubtfully distinct from the South American Euphorbia spathulata 

 Lam. 



6. Euphorbia alta Norton, North Amer. Euphorbia sect. Tith-vmalus 



24. 1899. 



Tithymalus altus (Norton) Woot. and Standi., Contrib. U.S. 

 Natl. Herbarium 16: 145. 1913. 



White Mountains (Apache County), Huachuca and Chiricahua 

 Mountains (Cochise County) , Santa Catalina and Santa Rita Moun- 

 tains (Pima County), up to 8,000 feet. New Mexico, Arizona, and 

 Mexico. 



7. Euphorbia chamaesula Boiss., Cent. Euphorb. 38. 1860. 



Euphorbia esulaeformis S. Schauer var.? subdentata Engelm. in 

 Torr., U. S. and Mex. Bound. Bot, 192. 1859. 



Euphorbia chamaesula Boiss. var. subdentata (Engelm.) Norton, 

 North Amer. Euphorbia sect. Tithymalus 47. 1899. 



Tithymalus chamaesula Woot. and Standi., Contrib. U. S. Natl. 

 Herbarium 16: 145. 1913. 



Apache, Navajo, and Coconino Counties to Cochise and Pima 

 Counties, 5,500 to 8,700 feet. New Mexico, Arizona, and Mexico. 



8. Euphorbia brachycera Engelm. in Torr., U. S. and Mex. Bound. 



Bot. 192. 1859. 



Tithymalus brachycerus Small, Fl. Southeast. U. S. ed. 2, 1349, 

 1375. 1913. 



Chiricahua, Mule, and Huachuca Mountains (Cochise County). 

 Texas to southeastern Arizona and Chihuahua. 



9. Euphorbia odontadenia Boiss. in DC, Prodr. 15 2 : 148. 1862. 



Segi Canyon (Navajo County). Otherwise known from the region 

 of El Paso, Tex. 



An uncertain entity closely allied to E. incisa. 



10. Euphorbia incisa Engelm. in Ives, Colo. River Rpt. 4: 27. 1860. 



Euphorbia schizoloba Engelm., Amer. Acacl. Arts and Sci. Proc. 5: 



173. 1861. 

 Tithymalus schizolobus Norton in Tidestrom, Contrib. U. S. 



Natl. Herbarium 25: 343. 1925. 



Coconino, Mohave, Gila, Maricopa, and Pinal Counties, 3,000 to 

 7,000 feet, type from Railroad Pass, Cerbat Mountains, Mohave 

 County (Newberry in 1858). Nevada, Arizona, and California. 



The var. mollis (Norton) L. C. Wheeler (E. schizoloba var. mollis 

 Norton, E. yaquiana Tidestrom), occurs in Yavapai, Graham, Gila, 

 Cochise, and Pima Counties, ascending to 9,200 feet, type from the 

 Santa Catalina Mountains (Pringle in 1881). It is distinguished from 

 the species in being pubescent throughout and usually more robust, 

 intergrading with E. palmeri var. subpubens and with E. robusta. 



11. Euphorbia palmeri Engelm. in S. Wats., Bot. Calif. 2: 75. 1880. 



Tithymalus palmeri Abrams, Fl. Los Angeles 216. 1917. 

 Euphorbia palmeri var. peplojolia Norton, North Amer. Eu- 

 phorbia sect. Tithymalus 41. 1899. 



Williams, Flagstaff, and San Francisco Peaks (Coconino County). 

 Utah and northern Arizona to California. 



