CACTUS FAMILY 577 



10. O. rhodantha K. Schum. Stem erect; internodes obovate or more 

 oblong, 7-12 cm. long, 5-10 cm. wide; pulvini with reddish brown bristles; 

 spines 2-4, soon becoming gray, up to 3 cm. long, the larger flattened, porrect or 

 erect, the lower deflexed; flowers carmine; style rose-red; stigma green; fruit 

 obovate, bristly, soon unarmed. Table-lands: Colo. w Xeb. Wyo. Submont. 

 Je. 



11. O. xanthostemma K. Schum. Stem erect, 3 dm. high; internodes 

 obovate, bright green; pulvini woolly at first, with reddish brown bristles; lower 

 ones spineless, the upper with 2-4 large spines, which are terete, 4 cm. long, the 

 upper dark brown, porrect, the lower reflexed, and 2-4 dark smaller ones; flowers 

 5 cm. broad, carmine-red; style white at the base; stigma green; fruit obovoid, 

 prickly. Table-lands: Colo. Submont. Je. 



12. O. basilaris Engelm. Ascending; internodes obovate, glaucescent, 

 minutely pubescent, 1-2 dm. long; pulvini depressed, with yellow wool and 

 numerous reddish brown bristles, without proper spines; flowers purple, 6 

 cm. broad; fruit short-obovate, pubescent. Desert regions: Ariz. Utah Xev. 

 se Calif. Sonora. Son. 



13. O. humifusa Raf. Stem diffuse; internodes obovate or suborbicular, 

 7.5-12 cm. long; pulvini with slender reddish brown bristles, mostly unarmed; 

 spines when present few, only marginal, stout, straight, white, usually reddish 

 at the base and apex, the longest 1.5-2.5 cm. long; flowers sulphur-yellow, 6-8.5 

 cm. broad; fruit clavate, naked, 3.5-5 cm. long, with purplish pulp. 0. Rafines- 

 quii Engelm. Sandy soil: Tex. Colo. Minn. Plain. 



14. O. Greenei Engelm. Stem diffuse; internodes orbicular-obovate; 

 pulvini with numerous reddish brown bristles, unarmed, or armed with 1-3 

 spines, the upper one stout, terete, 2.5-3.5 cm. long, brownish red, at least at the 

 base; fruit ovate, 3 cm. long, unarmed. Dry plains: Colo. Ariz. Son. Sub- 

 mont. 



15. O. tortispina Engelm. Stem prostrate; internodes orbicular-obovate, 

 1.5-2 dm. long; pulvini with yellowish bristles, armed with 3-5 yellowish, 

 angled, usually twisted spines, the longer ones 3-6 cm. long, with 2-4 slender 

 ones below; flowers sulphur-yellow, 6-7.5 cm. broad; fruit ovate, 4.5-5 cm. long. 

 Plains: Miss. Neb. Tex. Colo. Plain Son. 



16. O. camanchica Engelm. Stem prostrate; internodes obovate-orbicular; 

 pulvini with few greenish or yellowish brown bristles, armed with 1-3 (or the 

 marginal ones 3-6) spines, which are reddish brown or blackish brown, with 

 paler tips, 3.5-7.5 cm. long, the upper erect, the rest deflexed; fruit oval, 



cm. long, deep red, sweet. Plains and hillsides: Tex. Colo.- -Ariz. 

 Submoni. 



17. O. utahensis Purpus. Stem prostrate; internodes elliptic or obovate, 

 dark green; pulvini with yellowish white wool and yellowish bristles; spines 1-4, 

 the longest 4 cm. long; flowers up to 9 cm. broad, carmine; fruit cylindric, 4 cm. 

 long and 2 cm. thick. Mountains: Utah. Submont. 



18. O. Palmeri Engelm. Stem erect; internodes oval, not tuberculate, 

 pale, glaucous, 20-25 cm. long, 15-20 cm. broad; pulvini with pale brownish or 

 gray persistent wool, and few straw-colored bristles; spines 5-7 larger ones and 

 a few smaUer ones on the upper pulvini, 1-3 on the lower ones, : 



erect or spreading or the upper ones deflexed. Arid regions: s Ltah. 

 Je. 



19. O. rubrifolia Engelm. Prostrate; internodes ovate, 12-15 cm. long 

 and 10 cm. broad; pulvini with brownish gray persistent wool and numerous 

 yellowish bristles; spines mostly 2 or 3, slender, angular and often twisted, 1 

 m. long, all deflexed. Arid regions: s Utah. L. Son. 



2. ECHINOCEREUS Engelm. HEDGEHOG CEREUS. 



Plants with cylindric or rarely oblong stems, ribbed, or if tubercled, the 

 tubercles more or less connected in vertical rows. Leaves none. Spine-bearing 



