OPUNTIACEAE 817 



Fruits globose-obovoid. 9. O. Lindheimeri. 



Fruits club-shaped. 10. O. leptocarpa. 

 Spines brown, blackish or white. 



Spines several, white, spirally twisted. 11. O. tortispina. 



Spines 1 or 2, brownish black, straight. 12. O. fusco-atra. 



Spines none or imperfectly developed: corolla salmon-red. 13. O. inermis. 

 Joints readily separating when shocked: flowers small. 



Joints ovoid to obovoid : spines pale. 14. O. Pes-Corvi, 



Joints oblong to linear-oblong: spines dark brown at the tip. 15. O. Tracyi. 



Fruits dry. 16. O. polyacantha. 



Joints terete, slender. 17. O. leptocaulis. 



1. Opuntia Opuntia (L.) Coulter. Stems prostrate 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: fruits obovoid or clavate-obovoid, 2-3 cm. long: seeds 

 4 mm. wide or less, thick-margined. [0. vulgaris Mill.] 



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

 to fall. 



2. Opuntia Pollard! Britton & Eose. Stems prostrate, similar to those of 

 0. Opuntia in habit, the joints obovate, about 10 cm. long: bristle-cushion remote, the 

 lower ones of each joint unarmed: spines solitary in the bristle-cushion toward the 

 top of each joint, 2.5-4 cm. long: fruits short-obovoid, about 2.5 cm. long: seeds 5 

 mm. wide or more. 



Near Biloxl, Mississippi. 



3. Opuntia hnmifuaa Raf. Stems prostrate, from fibrous roots, diffusely 

 spreading, the joints obovate to suborbicular, 7.512 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: fruits club-shaped, 3.5 cm. 

 long, barely as thick with an edible purplish acid or sweetish pulp: seeds 5 mm. 

 broad, flattened, acutish margined. [0. Rafinesquei Engelm.] 



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



4. Opuntia Roseana Mackensen. Stems erect or ascending, from terete, more 

 or less tuberous roots, the joints thick, obovate to orbicular, 4-13 em. long, with 

 leaves 4-7 mm. long; bristle-cushions remote, the bristles pale yellow or whitish: 

 spines on the upper part of each joint, or wanting, slender twisted, solitary or 2 or 

 3 together, the upper ones erect or spreading, the lower one usually deflexed: flowers 

 pale yellow, except the claret-colored center, about 6 cm. broad: fruits obovoid-oblong 

 or elliptic-oblong, pink or rose-purple, 3.5-4.5 cm. long: seeds 2.5 mm. thick. 



In dry soil, southern Texas. 



5. Opuntia macrorhiza E'ngelm. 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: fruits 

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



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



6. 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: fruits 2.5-3 cm. long. 



In coral sand, southern peninsular Florida and the Keys. 



7. Opuntia grandiflora Engelm. Stems ascending, branching, the joints sub- 

 orbicular 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: fruits narrowly club-shaped, 6 cm. long: seeds 5-6 mm. broad. 



In sandy soil, along the Brazos River, Texas. 

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