242 CACTACE^E. cactus 



OPUNTIA. 



1. Cactus. Globose or oval plants without proper leaves, covered with 

 spine-bearing tubercles ; spines never barbed : flowers sessile, solitary, 

 from between the tubercles. 



2. Opuntia. Branching or jointed spiny plants with subulate [early 

 deciduous leaves : spines always barbed : flowers from the same areola 

 as the spines. 



1 CACTUS L. Sp. PI. 466. in part. 



MAMALARIA Haw. 



Roundish or somewhat cylindrical plants, destitute of woody 

 axis, often with a somewhat milky juice, covered with conical 

 or mammseform crowded spirally disposed tubercles which bear 

 deciduous spines and tomentum at their extremity. Flowers 

 sessile among the tubercles usually in a transverse zone. Tube of 

 the calyx adherent to the ovary, the lobes 5-6 crowning the 

 young fruit colored ; petals 5-6 scarcely distinct from the calyx, 

 longer than the sepals and united with them into a tube. Sta- 

 mens filiform, in several series. Styles filiform ; stigma 5-7- 

 cleft, radiate. Fruit smooth, 



C. viviparus Nutt. Fraser's Catalogue. Cespitose, the glomerules 

 subglobose : tubercles cylindric-ovate, bearded, marked above with a pro- 

 liferous groove; flowers bright red, large, exserted, exterior segments of 

 the calyx ciliate; fruit filiform, greenish. On summits of gravelly hills, 

 Eastern Oregon to British Columbia, east to Missouri. 



2 OPUNTIA Mill. Gard. Diet. ed. 6. 



Shrubby plants with articulate branches, the joints mostly 

 compressed and dilated, bearing fascicles of prickles or bristles- 

 arranged in a quincuncial or spiral order ; flowers arising from 

 the clusters of prickles or along the margin of the joints. Sepals 

 and petals numerous, adnate to the ovary, not produced into a 

 tube, the interior petaloid. Stamens numerous, shorter than 

 the petals. Style cylindrical constricted at the base, stigmas 

 numerous, thick, erect. Fruit umbilicate at the apex, tubercu- 

 late, often prickly. 



0. polyacantha Haw. Suppl. Succ. 82. 0. Missouriensis DC. Pros- 

 trate, forming large spreading masses: joints light-green, orbicular, tuber- 

 culate, 4-8 inches long: leaves minute, 2-3 lines long: pulvina 6-8 lines 

 apart, with reddish-brown bristles, all armed : spines 8-15, the 5-10 ex- 

 terior radiant, setiform, whitish or reddish variegated; the 3-5 interior ones 

 stout, reddish-brown, 1-2 inches long, 2-4 of them deflexed, the other one 

 spreading or suberect and very stout : flowers yellow or sometimes purple ; 

 stigmas 5-8 ; fruit ovate, dry and spiny, with shallow flat umbilicus, 1-2 

 inches long: seeds irregular, large. Plains and mountains, Eastern Wash- 

 ington to beyond the Rocky Mountains. 



Var. platycarpa Coulter Rev. Cact. 436. Joints elongated-obovate [to 

 obovate-orbicular, 3-5 inches long: pulvina 6-9 lines apart, with few 

 straw-colored bristles, the lower ones unarmed or upper ones with few 

 spines, or with exterior spines as in the species and mostly 1 stout spread- 

 ing or deflexed reddish-brown interior one : fruit depressed-globose with a 

 remarkably large and flat umbilicus, 4-9 lines long. Idaho to the Upper 

 Missouri. 



