986 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



21. Neomammillaria flavovirens (Salm-Dyck) Britt. & Rose, Cactaceae 4: 

 85. 1923. 



Manimillaria flavovirens Salra-Dyek, Cact. Hort. Dyck. 1849. 117. 1850. 



Mexico. 



Either solitary or somewhat cespitose, globose or short-cylindric, 6 to 8 cm. 

 high, light or yellowish green ; tubercles somewhat 4-angled ; axils naked ; 

 radial spines 5, slender, subulate ; central spines solitary, porrect ; flowers 

 white, streaked with rose. 



22. Neomammillaria sempervivi (DC.) Britt. & Rose, Cactaceae 4: 86. 1923. 

 MammiUaria sempervivi DC. Mem. Mus. Hist. Nat. 17: 114. 1828. 

 Mammillaria capiit-medusae Otto ; Pfeiff. Enum. Cact. 22. 1837. 

 Mammillarin diacantha Lem. Cact. Aliq. Nov. 2. 1838. 



Hidalgo and elsewhere in central Mexico. 



Solitary or somewhat cespitose, flattened above, narrowed below; axils of 

 tubercles very woolly, milky ; tubercles short, angled ; spine areoles very woolly 

 when young but glabrate in age ; radial spines 3 to 7, short, white, caducous ; 

 central spines 2, ascending, brownish, stoutish ; flowers dull white, with reddish 

 lines ; inner perianth segments acute, spreading. 



23. Neomammillaria obscura (Hildm.) Britt. & Rose, Cactaceae 4: 87. 1923. 

 MammiUaria obscura Hildm. Monatsschr. Kakteenk. 1: 52. 1891. 



Mexico, the range not known. 



Solitary, depressed-globose, blackish green ; axils woolly ; tubercles ar- 

 ranged in 13 and 21 spirals, angled, stout, woolly in the axils but not setose; 

 radial spines 6 to 8, subulate, white, unequal, the upper ones shorter than the 

 lower ; central spines 2 to 4, the lower one slightly curved, black ; flowers 

 small. 



24. Neomammillaria crocidata (Lem.) Britt. & Rose, Cactaceae 4: 87. 1923. 

 MammiUaria crocidata Lem. Cact. Aliq. Nov. 9. 1838. 



MammiUaria webbiana Lem. Cact. Hort. Monv. 45. 1839. 



Quergtaro and elsewhere in central Mexico. 



Plant globose or a little depressed, 5 to 6 cm. in diameter ; radial spines 6 

 or 7, dark brown or nearly black ; central spines none ; axils of tubercles in 

 young plant densely woolly; flowers from axils of old tubercles near top of 

 plant, reddish purple, 12 to 14 cm. long; outer perianth segments ciliate. the 

 inner acuminate. 



25. Neomammillaria polythele (Mart.) Britt. & Rose, Cactaceae 4: 88. 1923. 

 MammiUaria polythele Mart. Nov. Act. Nat. Cur. 16: 328. 1832. 

 Mammillaria quadrispina Mart. Nov. Act. Nat. Cur. 16: 329. 1832. 

 Mammillaria columnaris Mart. Nov. Act. Nat. Cur. 16: 330. 1832. 

 Mammillaria afflnis DC. Mem. Cact. 11. 1834. 



Mammillaria setosa Pfeiff. Allg. Gartenz. 3: 379. 1835. 



^Mammillaria hidalgensis Purpus, Monatsschr. Kakteenk. 17: 118. 1907. 



Hidalgo. 



Elongate, cylindric, often 30 to 50 cm. high, 7 to 10 cm. in diameter; tu- 

 bercles milky, in about 21 spirals, 10 to 12 mm. long, nearly terete, some- 

 what narrowed toward apex, dull green; axils of young tubercles densely 

 long-woolly and often nearly covering the top of plant, in age becoming 

 naked; spines 2 to 4, perhaps sometimes 6, all radial, somewhat spreading, 1 

 to 2.5 cm. long, reddish, straight or a little curved ; flowers from near the top 

 of the plant, reddish, 8 to 10 mm. long ; perianth segments narrow, acuminate ; 

 fruit red, clavate; seeds small, brownish. 



