598 MISC. PUBLICATION 4 2 3, U. S. DEFT. OF AGRICULTURE 



flowers, few strongly angled deep-green stems with 5 to 8 ribs, and spines 3 to 8 in 

 number, spreading, frequently all radial. 



2. Echinocereus coccineus Engelm. in Wisliz., Mem. North. Mex. 



94. 1848. 

 Eastern half of the State, mountains, 4,000 to 9,000 feet, common, 

 May to July. Colorado, Utah, New Mexico, and Arizona. 



3. Echinocereus mojavensis (Engelm. and Bigel.) Riimpler in Forst., 



Handb. Cact. ed. 2, 803. 1886. 



Cereus mojavensis Engelm. and Bigel. in Engelm., Amer. Acad. 

 Arts and Sci. Proc. 3: 281. 1856. 



Navajo, Coconino, and Mohave Counties, 4,000 to 6,000 feet. 

 Southern Utah and northern Arizona to southeastern California. 



4. Echinocereus rigidissimus (Engelm.) Rose, Contrib. U. S. Natl. 



Herbarium 12: 293. 1909. 



Cereus pectinatus var. rigidissimus Engelm., Amer. Acad. Arts 

 and Sci. Proc. 3: 279. 1856. 



Cochise, Pima, and Santa Cruz Counties, 4,000 to 6,000 feet, 

 rocky situations, June to August. Arizona and northern Sonora. 



Rainbow cactus. Central spines are wanting in E. rigidissimus. 

 Plants having 2 to 7 (usually 4 or 5) central spines have been collected 

 several times in southern Cochise County (Perilla Mountains, Harlan 

 in 1939). This form may be referable to E. pectinatus (Scheid.) 

 Engelm., although that rare species is known to occur only in Mexico 

 far from the boundary. 



Echinocereus dasyacanthus Engelm. has been reported from Arizona, but the 

 writers have not seen any Arizona material. This species has central spines and 

 large, lemon-yellow flowers. 



5. Echinocereus ledingii Peebles, Cactus and Succulent Jour. 8: 35. 



1936. 



Pinaleno Mountains, Graham County, the type locality, 4,500 to' 

 6,000 feet, May. Known only from Arizona. 



Specimens have been collected only from the type locality, but the 

 species is reported by Nichol as occurring also in mountain ranges in 

 Cochise and Pima Counties. 



6. Echinocereus engelmannii (Parry) Riimpler in Forst., Handb. 



Cact. ed. 2, 805. 1886. 



Cereus engelmannii Parry ex Engelm., Amer. Jour. Sci. ser. 2, 

 14: 338. 1852. 



Coconino and Mohave Counties to Pima and Yuma Counties, up 

 to 5,000 feet, common, February to May. Southern Utah to Sonora 

 and Baja California. 



A common and variable species. Ordinarily spines of more than 

 one color occur at the same areole, and they may be white, brown, 

 black, or yellow, opaque or rarely translucent. 



7. Echinocereus boyce-thompsoni Orcutt, Cactography 3: 4. 1926. 



(Reprinted in Amer. Jour. Bot. 25: 677. 1938.) 



Coconino, Yavapai, Gila, Graham, and Pinal Counties, 2,000 to 

 5,000 feet, April and May. Known only from Arizona. 



