'Genus 4. 



CACTUS FAMILY. 



573 



4. Opuntia polyacantha Haw. Many-spined Opuntia. Tuna. Fig. 2990. 



Cactus ferox Nutt. Gen. i: 296. 1818. Not 

 \V;ild. 1813. 



OfiiiiHa polyacantha Haw. Syn. PI. Succ. 

 Suppl. 82. 1819. 



Opuntia missounensis JJC Prodr. 3 ; 472. 1828. 



Prostrate, joints broadly obovate to or- 

 bicular, tubercled, pale gree; , 2-6' long, 

 about 6" thick, the tubercles 2" high, 

 densely spiny and with cushions of fine 

 bristles; spines 5-12, slender, 6"-2' long, 

 whitish ; leaves minute ; flowers light yel- 

 low, 2-3' broad; fruit dry, very prickly. 

 I'-ii' long. 



Plains and dry soil, Wisconsin to South Da- 

 kota, Athabasca. British Columbia, Nebraska, 

 Missouri, Utah and New Mexico. May-June. 



6. Opuntia fragilis (Xutt.) Haw. Brittle 

 Opuntia. Tuna. Fig. 2991. 



Cactus fragilis Nutt, Gen. i : 296. 1818, 



Opuntia fragilis Haw, Syn. PI. Succ. Suppl. 82. 1819. 



Decumbent or prostrate; joints ovoid. l'-2' long, 

 somewhat flattened or nearly terete. Leaves very 

 small, reddish; cushions composed of few bristles; 

 central spines 1-4, i'-ii long. S^ay, darker at the 

 apex, surrounded by 4-6 smaller ones ; flowers yel- 

 low, smaller than those of the preceding species ; 

 fruit nearly i' long, becoming dry at maturity, pro- 

 vided with cushions of bristles usually bearing a few 

 short spines. 



Prairies and dry soil, Iowa, Wisconsin and Minnesota 

 to South Dakota, British Columbia, Kansas and Utah. 

 July-Sept. 



7. Opuntia arborescens Engelm. Tree-cactus. 

 Fig. 2992. 



opuntia arborescens Engelm. Wisliz. Rep. 6. 1848. 



Erect, tree-like, 4-25 high, 4-8' in diameter at the 

 base, verticillately branched, the spiny branches spread- 

 ing or drooping. Joints verticillate, mostly in 3's or 

 4's, cylindric, 2'-6' long, less than t' in diameter, the 

 prominent tubercles 7"-io" long; leaves terete, spread- 

 ing, 6"-io" long; spines 8-30, terete, in yellowish 

 sheaths, diverging, the interior ones the longer, often 

 l' long or more; flowers purple, 2V-3' broad: fruit 

 subglobose, crested-tuberculate, dry, or nearly so, yel- 

 low, unarmed, about i' in diameter ; seeds smooth, 

 iJ"-2" wide 



Western Kansas, probably only in cultivation ; Colorado 

 to Texas, New Mexico, Arizona and Mexico, 



