57 2 



CACTACEAE. 



VOL. II. 



2. Opuntia humifusa Raf. Western Prickly Pear. Devil's Tongue. 



Fig. 2987. 



Cactus humifusus Raf. Ann. Nat. 15. 1820. 

 Opuntia humifusa Raf. Med. Bot. 2: 247. 1830. 

 O. mesacantha Raf. : Ser. Bull. Bot. Gen. 216. 1830. 

 O. Rafinesquii Engelm. Pac. R. R. Rep. 4: 41 1856. 



Prostrate, similar to the preceding specie.:; 

 joints obovate to suborbicular, or oval, usually 

 deep g re en, 2'-$' long; leaves subulate, spread- 

 ing, 3"-S" long; bristles reddish brown; spines 

 few, mostly near the margins of the joints, 1-4 

 together, whitish, or reddish at base and apex, 

 deflexed, or the longer one spreading and r-i 

 long; flowers yellow, often with a reddish centre, 

 2i'-3i' broad; petals 10-12; fruit club-shaped, 

 not spiny, fleshy, edible, iY-2 r long. 



In dry sandy or rocky soil, Ohio to Minnesota, 

 Kentucky, Missouri, Nebraska and Texas. Summer. 



Opuntia macrorhiza Engelm., a related species 

 with a deep woody root, abundant in Texas, is re- 

 ported to range northward into Missouri and Kansas. 



3. Opuntia tortispina Engelm. 



Twisted-spined Cactus. 



Fig. 2988. 



Opuntia tortispina Engelm. Pac. R. R. Rep. 



4: 21. 1856. 



Stems prostrate, the orbicular-obovate 

 flattened joints 6'-8' long. Spines 3-5, 

 yellowish, becoming whitish, angled and 

 channeled, sometimes twisted, the longer 

 ones i4'-2$' long, with 2-4 more slender 

 and shorter ones ; flowers sulphur-yellow, 

 2i'-3' broad ; fruit ovoid, fleshy, unarmed, 

 about 2' long and i' in diameter; seeds 

 orbicular, slightly notched at the hilum, 

 2"-3" wide. 



Plains of Missouri and Nebraska to Texas. 

 Summer. 



4. Opuntia camanchica Engelm. 

 Comanche Cactus. Fig. 2989. 



Opuntia camanchica Engelm. Pac. R. R. Rep. 

 4 : 40. 1856. 



Prostrate, with obovate-orbicular flat- 

 tened joints 6'-8' long, 5 '-8' wide. Spines 

 1-3, flattened, reddish brown to blackish, 

 ii'-3' long, or with 3-6 additional shorter 

 ones, the upper one suberect, the others 

 deflexed or spreading; flowers yellow, 

 about 2^' broad ; fruit oval, deep red, 

 juicy, i4'-2' long; seeds angular, mar- 

 gined, deeply notched at the hilum, 2" -3" 

 broad. 



Western Kansas (according to B. B. Smyth) ; 

 Colorado to Texas and Arizona. 



The plant of western Kansas differs from 

 the typical Texan one by having more slender 

 spines, lighter in color. It hybridizes with O. 

 fragilis. 



