972 CONTEIBUTIONS FEOM THE "NATIONAL HEKBARIUM. ; 



1. Escobaria tuberculosa (Engelm.) Britt. & Rose, Cactaceae 4: 54. 1923. 

 Mammillaria stroMliformis Scheer; Salm-Dyck, Cact. Hort. Dyck. 1849. 



104. 1850. Not M. stroUHformis Engelm. 1848. 



Mammillaria tuberculosa Engelm. Proc. Amer. Acad. 3: 268. 1856. 



Northern Mexico. Southwestern United States. 



Usually growing in clumps, cylindric, or becoming so, 5 to 18 cm. high, 

 2 to 6 cm. in diameter ; tubercles more or less regularly arranged in spirals, 

 6 mm. long; radial spines numerous, white, sometimes as many as 30, 

 acicular, 4 to 15 mm. long; central spines several, stouter than the radials, 

 brown to blackish or colored only at the tips, one of them usually porrect; 

 flowers 2.5 cm. in diameter when fully expanded, light pink ; outer perianth 

 segments acute, ciliate, the inner narrowly pointed ; fruit oblong, up to 20 

 mm. long, red ; seeds brownish, pitted, with a small ventral hilum. 



2. Escobaria dasyacantha (Engelm.) Britt. & Rose, Cactaceae 4: 55. 1923. 

 Mammillaria dasyacantha Engelm. Proc. Amer. Acad. 3: 268. 1856. 

 Northern Chihuahua. Texas and New Mexico, the type from El Paso. 

 Globose to short-oblong, usually 4 to 7 cm. in diameter but sometimes 20 



cm, long; radial spines 20 or more, white, bristle-like; central spines about 

 9, stouter and longer than the radials, the upper half usually reddish or 

 brownish, often 2 cm. long ; flowers pinkish ; perianth segments narrowly 

 oblong, apiculate ; fruit clavate, scarlet, 15 to 20 mm. long ; seeds black, 1 mm. 

 in diameter, slightly flattened, pitted, with a narrow white subbasal hilum. 



3. Escobaria chihuahuensis Britt. & Rose, Cactaceae 4: 55. 1923. 

 Chihuahua. 



Plants often solitary, perhaps also cespitose, globose to short-cylindric, 

 very spiny; tubercles short, usually hidden by the spines; radial spines 

 numerous, spreading; central spines several, longer than the radials, usually 

 brown or black in tlie upper part; flowers 1 to 1.5 cm. long, purple; outer 

 perianth segments broad, often rounded at apex, with ciliate margins; in- 

 ner perianth segments pointed. 



4. Escobaria runyonii Britt. & Rose, Cactaceae 4: 55. 1923. 

 Tj-pe from Reynosa, Tamaulipas. Texas. 



Cespitose, with numerous (sometimes 100) globose to short-oblong heads, 

 gray-green, 3 to 5 cm. long; tubercles 5 mm. long, terete in section, witli very 

 narrow groove above ; groove at first white-woolly, not glandular ; radial spines 

 numerous, acicular, white, 4 to 5 mm. long ; central spines stouter than the ra- 

 dials, 5 to 7, slightly spreading, with brown or black tips, 6 to 8 mm. long; 

 flowers 1.5 cm. long, pale purple, the segments with a dark purple stripe down 

 the middle, with pale margins; outer perianth segments narrow-oblong, with 

 thin ciliate margins, the inner narrower than the outer, with margins entire, 

 acute; fruit scarlet, globose to short-oblong, 6 to 9 mm. long, juicy. 



5. Escobaria chafEeyi Britt. & Rose, Cactaceae 4: 56. 1923. 

 Zacatecas, the type from Cedros. 



Short-cylindric, 6 to 12 cm. long, 5 to 6 cm. in diameter, almost covered 

 by the numerous white spines ; tubercles rather short, light green, with a nar 

 row groove above ; radial spines numerous, spreading, bristly ; central spines 

 several, a little shorter than the radials and brown or black-tipped; flowers 15 

 mm. long, cream-colored or sometimes purplish ; outer perianth segments ciliate, 

 the inner oblOng, obtuse, entire ; fruit crimson, 2 cm. long. 



