FLOWERING PLANTS AND FERNS OF ARIZONA 541 



The var. subpubens (Engelm.) L. C. Wheeler (E. subpubens Engelm., 



Tithymalus subpubens Norton), has a wider range in Arizona than the 

 typical form, occurring in the mountains of Coconino, Yavapai, Gila, 

 and Pima Counties, type from Prescott (Palmer 1 12 in 1876;. It differs 



from the species mainly in being pubescent. The specimens from 

 Gila and Pima Counties are not typical. 



12. Euphorbia lurida Engelm. in Ives, Colo. River Rpt. 4: 26. 1860. 



Euphorbia lurida var. pringL i Norton, North Amer. Euphorbia 



sect. Tithymalus 39. 1899. 

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



Herbarium 16: 145. 1913. 

 Tithymalus luridus pringlei Norton in Tidestrom, Contrib. 



U. S. Natl. Herbarium 25: 343. 1925. 



Apache, Coconino, Yavapai, Greenlee, Graham, and Cochise Coun- 

 ties, 3,500 to 7,000 feet. Southern Utah, New Mexico, and Arizona. 



13. Euphorbia robusta (Enselm.) Small in Britton and Brown, Illus. 



FJ. 2:381. 1897/ 



Euphorbia montana Engelm. var. robusta Engelm. in Torr. 



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

 Euphorbia montana Engelm., ibid. Not Raf., 1817. 

 Tithymalus robustus Small in Rvdb., Colo. Agr. Expt. Sta. 



Bui. 100: 224. 1906. 

 Tithymalus montanus Small, ibid. 

 Tithymalus philorus Cockerell, Muhlenbergia 4: 56. 1908. 



Camp Grant (Graham County), Mazatzal Mountains (Gila 

 County), 4,800 to 5,500 feet. South Dakota, Montana, and Utah to 

 New Mexico and Arizona. 



14. Euphorbia marginata Pursh, Fl. Amer. Sept. 2: 607. 1814. 



Dichrophyllum marginatum (Pursh) Klotzsch and Garcke, 

 Abhandl. Preuss. Akad. Wiss. Phvs.-Math. Kl. 1859: 44. 

 1860. 



Gila Valley (Graham? County), Fort Huachuca (Cochise County). 

 Montana south to southern Mexico, widely introduced east of the 

 Mississippi River. 



Snow-on-the-mountain. Three different collectors found this in 

 Arizona before 1900, but no recent collections seem to have been made. 



15. Euphorbia plummerae S. Wats., Amer. Acad. Arts and Sci. Proc. 



18: 195. 1883. 

 Known, in Arizona, only from the type collection from Tanner 

 Canyon, Huachuca Mountains, Cochise County (Lemmon 2874). 

 Southeastern Arizona, Chihuahua, and Sonora. 



16. Euphorbia bilobata Enselm. in Torr., U. S. and Mex. Bound. Bot. 



190. 1859. 



Zygophyllidium bilobatum Standi., Contrib. U. S. Natl. Herbad- 

 rium 13: 199, 227. 1910. 



Yavapai, Greenlee, Cochise, and Santa Cruz Counties, 3,600 to 

 6,000 feet. Western Texas to Arizona. 



