FLOWERING PLANTS AXD FERNS OF ARIZONA 539 



1. Euphorbia radians Benth., PI. Hartw. 8. 1839. 



Poinsettia radians (Benth.) Klotzsch and Garcke, Monatsber. 

 Preuss. Akad. Wiss. Phys.-Math. Kl. 1859: 253. 1859. 



Huachuca Mountains (Cochise County), Rosemont and south of 

 the Santa Rita Mountains (Pima County). Western Texas to south- 

 ern Arizona and Mexico. 



2. Euphorbia eriantha Benth., Bot. Voy. Sulph. 51. 1844. 



Poinsettia eriantha (Benth.) Rose and Standi., Contrib. U. S. 

 Natl. Herbarium 16: 13. 1912. 



Graham, Maricopa, Pinal, Pima, and Yuma Counties, 300 to 3.700 

 feet, dry hot slopes and canyons. Texas to southeastern California 

 and northern Mexico. 



3. Euphorbia dentata Michx., Fl. Bor. Amer. 2: 211. 1803. 



Poinsettia dentata (Michx.) Klotzsch and Garcke. Monatsber. 



Preuss. Akad. Wiss. Phys.-Math. Kl. 1859: 253. 1859. 

 Euphorbia dentata var. rigida Engelm. in Torr., U. S. and 

 Mex. Bound. Bot. 190. 1859. 

 Greenlee, Cochise, Santa Cruz, and Pima Counties, 3.000 to 8,000 

 feet. Eastern United States to Utah, southern Arizona, and Mexico. 

 The var. cuphosperma Engelm. has been collected in southern 

 Apache, Cochise, Santa Cruz, and Pima Counties, type from Cochise 

 County (Wright in 1851). It differs from the species in having sharply 

 quadrangular seeds, strigose capsules, and shallowly toothed to entire 

 often lanceolate to linear leaves, whereas the typical form has ovoid 

 seeds, glabrous capsules, and generally coarsely toothed, mostly ovate- 

 lanceolate to obovate-cuneate leaves. The var. gracilUma Millsp. 

 is unworthy of recognition. It is intermediate between var. cuphos- 

 perma and the species. The type came from Bowie. 



4. Euphorbia heterophylla L., Sp. PL 453. 1753. 



Poinsettia heterophylla Klotzsch and Garcke, Monatsber. 

 Preuss. Akad. Wiss. Phys.-Math. Kl. 1859: 253. 1859. 



Cochise, Santa Cruz, and Pima Counties, 2,500 to 5.200 feet. 

 Southeastern United States to southern Arizona, south to tropical 

 America. 



Painted spurge. The plants referred here differ in the angled seeds 

 from the plants to which the name is usually applied. The Arizona 

 plants may represent another, perhaps undescribed, species but 

 decision must await a careful revision of a group of plastic tropical 

 species. The floral leaves are often partly colored pink or red. 



5. Euphorbia dictyosperma Fisch. and Mever, Index Sem. Hort. 



Petrop. 2: 37. 1836. 

 Euphorbia arkansana Engelm. and Grav, Boston Jour. Nat. 



Hist. 5: 261. 1845. 

 Euphorbia arkansana var. missouriensis Norton, North Amer. 



Euphorbia sect. Tithymalus 19. 1899. 

 Euphorbia arkansana var. atrosemina Norton, ibid. p. 21. 

 Tithymalus missouriensis (Norton) Small, FL Southeast. U. S. 



721, 1334. 1903. 

 Tithymalus dictyospermus Heller, Muhlenbergia 1: o(S. 1904. 

 Yavapai, Gila, Pinal, and Pima Counties, 1,300 to 5,000 feet. 

 Widely distributed in the United States and northern Mexico. 



