STANDLEY TEEES AND SHRUBS OF MEXICO. 971 



Plants usually solitary, globular to short-oblong, 8 to 12 cm. long, the 

 whole body usually hidden under a mass of spines; radial spines numerous, 

 acicular, usually white; central spines several, much stouter than the radials, 

 pale below, brown or black toward the top; flowers 4 to 5 cm. broad when 

 fully expanded ; outer perianth segments greenish or the ones nearer the 

 center purplish, ciliate; inner perianth segments broadly linear, acuminate 

 and apiculate, more or less serrate above; fruit 2.5 cm. long, green, juicy, 

 naked except a few hairy scales near the top, capped by the withered perianth, 

 depressed at apex. 



30. Coryphantlia aggregata (Engelm.) Britt. & Rose, Cactaceae 4: 47. 3923. 



MammiUaria aggregata Engelm. in Emory, Mil. Reconn. 157. 1848. 



Sonora. Arizona, the type fi-om the headwaters of the Gila. 



Plants solitary or cespitose, globular to short-oblong, very spiny; radial 

 spines numerous, white, often with brown tips, appressed ; central spines sev- 

 eral, stout, all erect and appressed or one often porrect, those toward the top 

 of the plant connivent; flowers very large and showy, purplish, 5 to 7 cm. 

 broad ; outer perianth segments ciliate, the inner narrowly oblanceolate, often 

 6 mm. broad, acuminate ; fruit green, oblong, 2 to 2.5 cm. long, naked or occa- 

 sionally bearing a small scale on the side, juicy; seeds dark brown, 2 mm. 

 long. 



DOUBTFUL SPECIES. 



The following plants, described as species of MammiUaria, probably belong 

 to this genus. 



Mammillaria coedigera Hesse, Gartenflora 59: 445. 1910. Doubtless a native 

 of Mexico. 



Mammillaria cornuta Hildmann ; Schum. Gesamtb. Kakt. 496. 1898. Native 

 of Mexico. 



Mammillaria potosiana Jacobi, AUg. Gartenz. 24: 92. 1856. Type from 

 San Luis Potosf. 



Mammillaria recurvispina De Vriese, Tijdschr. Nat. Gesch. 6: 53. 1839. 

 Described from Mexico. 



45. ESCOBARIA Britt. & Rose, Cactaceae 4: 53. 1923. 



Globose or cylindric, usually cespitose cacti, never milky ; tubercles grooved 

 above, persisting as knobs at the base of old plants after the spines have 

 fallen ; spines both central and radial, never hooked ; flowers small, regular, 

 appearing from tbe top of the plant at the bottom of the groove of young 

 tubercles; stamens and style included; fruit red, naked (or with one scale), 

 indehiscent, globular to oblong, crowned by the withering perianth ; seeds 

 brown to black, the aril basal or subventral. oval. 



Two other species occur in Texas. 



Outer perianth segments not ciliate 6. E. lloydii. 



Outer perianth segments ciliate. 

 Flowers 2 to 2.5 cm. long. 



Plants elongate; seeds small, brown 1. E. tuberculosa. 



Plants usually globose ; seeds larger, black 2. E. dasyacantha. 



Flowers 1.5 cm. long. 



Inner perianth segments pointed. 



Inner perianth segments broad 3. E. chihuahuensis. 



Inner perianth segments narrow 4. E. runyonii. 



Inner perianth segments obtuse 5. E. chaffeyi. 



