816 OPUNTIACEAE 



colored to red, straight or curved, deflexed or spreading : flowers yellow within, red with- 

 out, 6-7.5 cm. broad: fruit globose-obovoid or nearly so, 5 cm. long, purplish without, the 

 pulp insipid or nauseous : seeds 3-4 mm. long, margined. 

 In valleys, Texas to California and Mexico. 



4. Opuntia tortispina Engelm. Stems procumbent, the branches ascending, the 

 joints orbicular-obovate, 15-20 cm. long, with cushions or yellowish bristles, 2.5-3.5 cm. 

 distant: spines white, 3-5 together, 3.5-6 cm. long, angled, channeled, often spirally 

 twisted, accompanied by 2-4 spines about as long, below them : flowers sulphur-yellow, 

 6-7.5 cm. long : seeds suborbicular, 4-6 mm. broad. 



On plains, Nebraska to the Indian Territory and Texas. 



5. Opuntia grandiflora (Engelm.) Small. Stems ascending, branching, the joints 

 suborbicular to obovate, 12-15 cm. long, bright green : bristle-cushions remote, the bristles 

 slender : spines sometimes wanting or obsolete : flowers yellow except the red center, 11- 

 12.5 cm. broad: fruit narrowly club-shaped, 6 cm. long: seeds 5-6 mm. broad. [0. 

 Rafinesquei var. grandiflora Engelm. ] 



In sandy soil, along the Brazos River, Texas. 



6. Opuntia macrorhiza Engelm. Stems prostrate or ascending from fusiform or 

 thick-tuberous roots, the joints narrowly obovate or oblong-obovate, bright green, 5-8 

 cm. long, with small leaves about 10 mm. long : bristle-cushions remote, near the base or 

 margins of the joints, the bristles yellowish brown : spines scattered over the joints or 

 chiefly near the top, solitary or 2-3 together, white or variegated, slender, spreading or 

 deflexed : flowers pale yellow, red at the base, 5-7.5 cm. broad : fruit obovoid, green or 

 pale purple, 3.5 cm. long : seeds 5 mm. thick, acute-margined. 



In sterile soil, Kansas to Arkansas, Texas and Arizona. 



7. Opuntia austrina Small. Stems more or less spreading, shrubby at the base, from 

 tuberous roots, the joints broadly obovate or orbicular-obovate, deep green, 5-11 cm. long, 

 or rarely somewhat longer, with early deciduous leaves mostly less than 10 mm. long : 

 bristle-cushions chiefly near the margins of the joints, the bristles sordid or tawny : spines 

 above the middle of the joints and near the edge, usually 2 together but one of them very 

 small or deciduous, whitish or pinkish and reddish near the base and apex, twisted : 

 flowers bright yellow, 6-7 cm. broad : petals cuneate, truncate or retuse at the slightly 

 eroded top, and mucronate : fruit 2.5-3 cm. long. 



In coral sand, southern peninsular Florida and the Keys. 



8. Opuntia humifusa Raf. Stems prostrate, from fibrous roots, diffusely spreading, 

 the joints obovate to suborbicular, 7.5-12 cm. long, deep green, with subulate leaves often 

 6-8 mm. long : bristle-cushions remote, with reddish brown bristles, usually unarmed, or 

 spines few, straight, whitish or often reddish at the base and apex, terete, mostly marginal, 

 1.5-2. 5 cm. long, straight : flowers sulphur-yellow and often reddish in the center, 6-8.5 

 cm. broad : fruit club-shaped, 3.5 cm. long, barely J as thick with an edible purplish acid 

 or sweetish pulp: seeds 5 mm. broad, flattened, acutish margined. [O. Rafinesquei 

 Engelm.] 



In sandy or rocky soil, Minnesota to Missouri, Kentucky and Texas. 



9. Opuntia fusco-atra Engelm. Stems diffusely branched, the joints orbicular- 

 obovate, 6-7. 5 cm. long, tuberculate : bristle-cushions rather remote, tomentose, the upper 

 one unarmed, the bristles reddish brown : spines brownish black, usually solitary, 2.5-3 

 cm. long, short, rather erect, an additional short deflexed one sometimes present : flowers 

 yellow, 7.5 cm. broad : fruit unknown. 



In sterile soil or on prairies, Texas. 



10. Opuntia Opuntia ( L. ) Coulter. Stems prostrate or diffusely ascending from 

 fibrous roots, the joints orbicular to obovate, pale or light green, 5-10 cm. long, bearing 

 thick leaves 4-5 mm. long : bristle-cushions rather remote, usually unarmed : bristles few, 

 yellowish green : spines few, when present solitary, less than 2.5 cm. long, variegated: 

 flowers pale yellow, 5-6 cm. broad : fruit obovoid or clavate-obovoid, 2-3 cm. long : seeds 

 5 mm. long, thick-margined. [0. vulgaris Mill.] 



In sand or sandy soil, or on rocks, Massachusetts to Florida and Alabama. Spring to fall. 



11. Opuntia Pfes-Corvi LeConte. Stems prostrate or diffusely spreading, 3-7 dm. 

 long, the joints narrowly ovoid to obovoid, nearly terete, 2.5-7.5 cm. long, light green, 

 loosely attached to each other : bristle-cushions quite numerous, the upper ones armed, the 

 bristles pale : spines slender, solitary or 2-3 together, straight, 2.5-3.5 cm. long, often flat- 

 tened at the base and twisted : flowers yellow, 3.5-4 cm. broad : fruit obovoid, 12-15 mm. 

 long, rose-purple, bristly : seeds often 4-5 mm. long, with an obtuse margin. 



On sandy coasts or adjacent ridges, Georgia and Florida. 



