448 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Only 1 central spine in each areole hooked; radials 



15 to 30 3. M. grahami. 



More than 1 central hooked in some of the areoles; 



radiate 8 to 12 4. M. wrightii. 



None of the spines hooked, the centrals usually 1, some- 

 times wanting; plants flat-topped, with turbinate 

 root and milky juice. 



Radial spines few, 5 to 9, stout, dull-colored 5. M. meiacantha. 



Radials more numerous, 10 to 20, slender, white 6. M. heyderi. 



Tubercles grooved on the upper side (iu M. macromeris the groove 



wanting in young plants and never reaching the axil); none 



of the spines hooked. 



Central spines none or 1; plants small, subglobose, 2 to 5 cm. 



high; radials very numerous, 30 to 50, 5 to 10 mm. 



\ ons 7. M. dasyacaniha. 



Centrals several, generally 3 or more; plants larger, of various 



shapes; radials various. 



Tubercles large, 12 to 35 mm. long (mostly about 20 mm.); 



plants large, with long spines. 



Flowers rose purple; central spines mostly 4, dark, 



slender but strong, 2 to 5 cm. long; plants 



cespitose 8. M. macromeris. 



Flowers brownish yellow; centrals 2 to 5, light-colored, 



stout, 2 to 3 cm. long (one usually curved 



downward at the tip); plants mostly solitary. . 9. M. scheerii. 



Tubercles smaller, usually less than 12 mm. long; plants 



small, with relatively short and numerous spines. 



Fruit bright red; lower spines deciduous, leaving 



the base of the plant tuberculate with dry 



corky protuberances; spines numerous, white; 



centrals 5 to 9, glaucous, purple-tipped 10. M. tuberculosa. 



Fruit green; lower spines rarely deciduous; base of the 

 plant little or not at all tuberculate; spines 

 numerous, but the centrals mostly darker 

 and not quite so numerous (except in M. 

 radiosa neomexicana) . 

 Stigmas short-mucronate; plants proliferous and 



cespitose; seeds yellowish brown 11. M. vivipara. 



Stigmas obtuse; plants sparingly proliferous, 

 iisually solitary; seeds reddish brown, 

 slightly larger 12. M. radiosa. 



The references by Coulter ' of Cactus scolymoides and C. echijius to New Mexico 

 are probably dependent upon an incorrect determination of Mamillaria scheerii, for 

 the former at least; and he does not cite any specimens of the latter species, although 

 including it in our range. We have seen no specimens of either species from New 

 Mexico. 



1. Mamillaria micromeris Engelm. Proc. Amer. Acad. 3: 260. 1856. 



Type locality: "From El Paso eastward to the San Pedro River," Texas. 



Range: Western Texas and southern New Mexico. 



New Mexico: Sacramento Mountains; Guadalupe Mountains; Capitan Mountains. 

 Dry limestone mountains, in the Lower and Upper Sonoran zones. 



1 Contr. U. S. Nat. Herb. 3: 115, 116. 1896. 



