580 CACTACEAE 



4. E. pubispinus Engelm. Small, turbinate or ellipsoid, 5 cm. high, 2.5-3 

 cm. in diameter; ribs 13, compressed, tuberculate ; spines velvety pubescent, in 

 age glabrate; radial spines 5-6 below, 9-12 above, 2-8 mm. long, straight to hooked; 

 central spines wanting or solitary, longer, 10-12 mm. long, strongly hooked. 

 Valleys: Utah. Son. 



5. E. cylindraceus Engelm. Globose to ovoid or ovate-cylindric, simple 

 or branching at the base, up to 9 dm. high and 3 dm. thick; ribs 13-27, obtuse and 

 tuberculate; spines stout, compressed, more or less curved, reddish; radials 

 about 12, 2.5-5 cm. long, the lowest stouter and hooked; centrals 4, very stout, 

 4-angled, about 5 cm. long, the uppermost broadest, straight and erect, the 

 lowest decurved; flowers yellow; fruit subglobose, pale green, 2.5 cm. thick. 

 Desert regions: Tex. s Utah Calif. L. Calif. L. Son. 



6. E. Wislizeni Engelm. At first globose, at last cylindric, 5-12 dm. high; 

 ribs 21-25, or sometimes less, acute and oblique, more or less tubercled; radial 

 spines 1.5-5 cm. long, the 3 upper and 3-5 lower stouter, the lateral ones bristle- 

 like; centrals 4, stout, angled, red, 3.5-7.5 cm. long, the 3 upper straight, the 

 lowest and strongest up to 12 cm. long, flat and hooked downwards; flowers 

 yellow or sometimes red, 5-6.5 cm. long; fruit ovate, yellow. Desert regions: 

 w Tex. s Utah Calif. ; n Mex. L. Son. 



7. E. subglaucus Rydb. Simple, depressed-globose or ellipsoid; ribs 8-13, 

 with conical tubercles; radial spines 8-9, white or with darker tips, straight, up 

 to 15 mm. long; central spines 1-3, curved, dark brown; flowers 3 cm. broad, 

 rose-red; fruit pear-shaped, 1 cm. high. E. glaucus K. Schum., not Karw. 

 High table-land: Colo. Submont. 



8. E. Johnson! Parry. Stem oval, 1-1.5 dm. high; ribs 17-21, rounded, 

 interrupted into low rounded tubercles; radial spines 10-14, 1.5-3 cm. long, the 

 upper strongest; central spines 4, stout, recurved, reddish gray, 3.5-4 cm. long; 

 flowers 5-6.5 cm. long, deep red to pink; seeds pitted. Arid regions: Utah. 

 Son. 



9. E. Sileri Engelm. Globose; ribs 13, prominent, densely crowded with 

 short rhombic-angled tubercles; radial spines 11-13, white; centrals 3, black with 

 pale base, 18 mm. long, the uppermost slightly longer; flowers scarcely 2.5 cm. 

 long, straw-colored. Desert regions: s Utah. L. Son. 



4. PEDIOCACTUS Britton & Rose. 



Stem globose, leafless, tubercled; the tubercles arranged in spiral rows, 

 nipple-shaped. Flowers borne on the tubercles, near the areolae. Hypanthium 

 funnelform, bearing a few scales. Petals numerous, pink. Stamens numerous. 

 Fruit globose, irregularly bursting, nearly or quite scaleless. Seed tubercled, 

 with a basal hilum. 



1. P. Simpson! (Engelm.) Britton & Rose. Subglobose or turbinate at the 

 base, sometimes clustered, 7.5-12.5 cm. in diameter; ribs 8-13, with prominent 

 nipple-shaped tubercles, which are 12-16 mm. long; radial spines 20-30, slender, 

 straight, 8-12 mm. long; central spines 8-10, stouter, yellowish to black, 10-14 

 mm. long; flowers 16-20 mm. long, and nearly as broad, yellowish green or 

 purple; fruit green, 6-7 mm. long, suborbicular. Echinocactus Simpsoni Engelm. 

 Table-lands and plains: Nev. Utah Colo. Submont. Subalp. 



5. CORYPHANTHA (Engelm.) Lem. 



Fleshy plants, with globular or oval, solitary or clustered stems, covered by 

 spirally arranged tubercles with spine-bearing areolae at the end. Leaves none. 

 Flowers borne near woolly areolae in the axils or near the base of the tubercles. 

 Hypanthium produced oeyond the ovary, campanulate or funnelform, naked. 

 Style filiform. Berry fleshy. [Mamillaria Haw.] 



Larger spines curved upwards; tubercles not grooved; flowers borne at the base of older 



tubercles, hence lateral on the stem. 1. C. Grahami. 



Spines all straight; tubercles grooved; flowers borne at the base of young tubercles, hence 

 nearly terminal. 



