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



7. Juice clear; stem cylindric, ovoid, or hemispheric; some of the spines hooked 



(rarely so in M. oliviae); seeds black or dark brown, commonly opaque, 



when pitted the depressions circular or somewhat angled but not elongate 



(9). 



9. Central spines rarely hooked, usually straight and short; stem ovoid to 



cylindric; berry clavate, scarlet, 20 to 25 mm. long; seeds black, pitted. 



11. M. OLIVIAE. 

 9. Central spines hooked (10). 



10. Seeds coarsely rugose and finely reticulate, dark brown, 2 mm. long, 



the hilum greatly enlarged, corky, light brown; stem ovoid to 



cylindric; berry obovoid-clavate, scarlet, 10 to 20 mm. long; central 



spines 1 to 4 at an areole, 1 or all hooked__ 7. M. tetrancistra. 



10. Seeds smaller, pitted, the hilum not enlarged (11). 



11. Spines yellow; stem hemispheric; berry obovoid, scarlet or red, 5 to 



7 mm. long 8. M. mainae. 



1 1 . Spines not yellow, in various combinations of white and dark reddish 

 " brown (12). 

 12. Plants colonizing freely; stem flaccid, rarely more than 12 cm. 

 long and 3 cm. in diameter; berry obovoid to clavate, scarlet ; 



7 to 13 mm. long 9. M. fasciculata. 



12. Plant solitary; stem rarely less than 5 cm. in diameter (13). 



1 3. Berry scarlet, clavate, 12 to 25 mm. long; stem ovoid to cylindric, 

 firm; perianth segments spreading, pink with white margin; 



spines glabrous 10. M. microoarpa. 



13. Berry green or purplish, ovoid to subglobose, 10 to 15 mm. in 

 diameter, borne at or near the apex of the stem; perianth 

 segments erect with spreading tips, pink, straw-colored, or 

 greenish white; stem hemispheric to cylindric, flaccid; spines 

 glabrous or pubescent 12. M. wilcoxii. 



1. Mammillaria recurvata Engelm., Acad. Sci. St. Louis Trans. 2: 202. 



1863. 



Coryphantha recurvata Britt. and Rose, Carnegie Inst. Wash. 

 Pub. 248. 4: 27. 1923. 



Pajarito Mountains, Santa Cruz County, about 4,500 feet, July. 

 Arizona and Sonora. 



A single plant may have as many as 50 stout stems. 



2. Mammillaria engelmannii Cory, Rhodora 38: 405. 1936. 



Echinocactus muehlenpfordtii Poselger, Allg. Gartenztg. 21: 

 102. 1853. (Not Mammillaria muehlenpfordtii Forst. 

 1847.) 



Coryphantha muehlenpfordtii Britt. and Rose, Carnegie Inst. 

 Wash. Pub. 248. 4: '28. 1923. 



Paradise to San Simon, Cochise County, about 4,000 feet (Loomis 

 and Peebles S. F. 200), July. Western Texas, southern New Mexico, 

 Arizona, and northern Mexico. 



The stem is large for the genus, occasionally attaining a height of 

 about 30 cm. 



3. Mammillaria robustispina Schott ex Engelm., Amer. Acad. Arts 



and Sci. Proc. 3: 265. 1856. 



Coryphantha robustispina Britt. and Rose, Carnegie Inst. 

 Wash. Pub. 248. 4: 33. 1923. 



Cochise, Pima, and Santa Cruz Counties, 2,500 to 6,000 feet, 

 July. Arizona and northern Sonora. 



