OPUNTIA 



OPUNTIA 



1151 



in diam., having a thick, grayish, scaly, unarmed bark: 

 joints congested toward the ends of the larger branches, 

 ovate to ovate-cylindrical, 2-8 in. long and often 2 in. 

 thick, very fragile and tumid, easily becoming detached 

 and taking root, bluish green, somewhat glaucous : areo- 

 Ise with white wool and bright straw-colored bristles; 

 spines on young growth 5-8, increasing yearly until 

 ultimately 30-50, finally deciduous, with loose, glisten- 

 ing, white or straw-colored sheaths 1% in. or less long: 

 fls. %-l in. wide, pink : fr. obovate to globose, light 

 green, pendulous, in large, proliferous clusters, some- 

 times 50 in a single cluster. Southwestern U. S. and 

 North Mexico. The common "Cholla" of the Arizona 

 plains, where it often becomes a fair-sized tree and nota- 

 ble for its formidable armor of barbed spines completely 

 hiding the surface of the plant. 



Var. mamillata, Coult. Differs in having fewer, 

 shorter spines. 



52. Bigeldvii, Engelm. An erect, compact plant, 4-6 ft. 

 high, rarely higher, with fragile woody skeleton which 

 does not appear in joints of the first year's growth, the 

 most densely spine-covered and difficult to handle of 

 the cylindrical Opuntias : joints readily detached and 

 forming formidable burs, ovate, short elliptical to long 

 and cylindrical, with rounded ends, readily breaking 

 from the plant and taking root, pale green, fragile, tu- 

 mid, terminal ones frequently 3-5 in. long and half as 

 thick : areolae close together, with white wool and pale 

 yellow bristles ; spines 10-20, some very small, increas- 

 ing in number as stems become older, straw-colored, 

 loose-sheathed, 1 in. or less long, completely hiding the 

 surface of the plant: fls. greenish red, 1 in. broad: fr. 

 very spiny, ovate, lJ^-2 in. long and one-third as wide, 

 few-seeded, mostly sterile. Ariz., Calif. 



53. imbricata, P. DC. A wide-spreading, irregularly 

 branching shrub, rarely more than 5 ft. high, the trunk 

 and larger branches with dark, rough, unarmed bark: 

 joints frequently 12 or 14 in. long and 1-1% in. thick, 

 with very prominent long, cristate tubercles : areolae 

 with yellowish wool and straw-colored bristles ; spines 

 2-5, of variable length, 1 in. or less long, loosely 

 sheathed, white to straw-colored: fls. 2-2% in. wide, 

 light purple : fr. unarmed, depressed globose, with large 

 tubercles, yellow, 1-1% in. in diam., adhering to the 

 plant and drying on the stems during the winter. Tex. 

 and northern Mex. Usually confused with 0. arbores- 

 cens, from which it differs in its smaller growth, differ- 

 ent habit, much longer joints, larger, more prominent 

 tubercles, and fewer spines. The fruit and flower also 

 show marked differences. 



54. arbor6scens, Engelm. (O.steU(lta,$a,lm.). An arbor- 

 escent, numerously-branched plant, 4-8 ft. high, with 

 trunk of larger plants having very rough, dark, unarmed 

 bark: joints with moderately prominent, narrow, cristate 

 tubercles, verticillate, horizontally spreading on mostly 

 pendulous, moderately spiny branches, mostly 3-6 in. 

 long and ] in. or less thick: areolae with dirty-white 

 wool and small yellow to light brown bristles; spines 

 6-LM, variable in length, 1 in. or less, central ones more 

 loosely sheathed, horny or reddish brown, white to 

 strasv-colored sheaths : fls. purple, 2-3 in. wide: fr. 

 unarmed or with few spines, conspicuously tuberculate, 

 subglobose, 1 in. in diam., yellow to yellowish red. 

 Southwest U. S. Frequently "confused with O. imbri- 

 cata and O. spinosior, intermediate between the two. 

 Differs from the latter in having much larger, more 

 cristate tubercles, fewer spines and different fruit. 



55. spindsior, Tourney. A small tree, 6-12 ft. high, 

 with numerous verticillate branches, forming a rounded 

 head, the cylindrical trunk usually branching a few 

 feet above the ground, and with rough, dark brown or 

 grayish unarmed bark : joints verticillate and pendulous, 

 ultimate ones usually 4-8 in. long and about 1 in. thick, 

 dark green, frequently more or less purplish, with 

 short, crowded rhombic tubercles : areolae with white to 

 reddish brown wool and usually few, small, variously 

 colored bristles; spines 10-30, increasing in number 

 yearly as the joints become older until finally deciduous, 

 short* and rarely conspicuously sheathed, usually %-/ 

 in. long: fls. showy, bright to dark purple, 2-2% in. 

 wide, in whorls at the ends of the joints : fr. elliptical to 

 oblong, rarely obovate to globose, l%-2% in. long, yel- 



low, frequently remaining on the stems during the sec- 

 ond year. Ariz., northern Mex. 



56. Whipplei, Engelm. and Bigel. A spreading, sub- 

 prostrate shrub, rarely exceeding 2 ft. in height, with 

 numerous ascending secondary branches, having short, 

 crowded, prominent tubercles: joints variable, terminal 

 ones clavate, 2-5 in. long and %-% in. thick, mostly 

 armed on upper half: areolae with short white wool and 

 a few short, light-colored bristles ; spines white, very 

 variable, on terminal joints, usually from 1-3 con- 

 spicuous loose - sheathed interior ones and several 

 small, deflexed or radiating ones: fls. greenish yellow, 

 crowded at the ends of the joints, 1-1% in. wide: fr. 

 unarmed or with few spines, pyriform to subglobose, 

 densely tuberculate, yellow or tinted with scarlet, %-l 

 in. in diam., drying and remaining attached to the plant 

 during the winter. Southwest U. S. and northwest Mex. 

 This plant is frequently confused with O. spinosior, 

 probably from confusion in the original description. 



57. versicolor, Engelm. A small, numerously branched 

 tree, 6-10 ft. high, with rounded head and a short trunk, 

 having smooth, light brown or reddish brown, unarmed 

 bark: joints much elongated, usually 6-12 in. long, some- 

 times 20, %-% in. thick, deep green, more or less colored 

 with red and purple : areolae with short gray wool and 

 lighter colored bristles; spines variable, on terminal 

 joints, usually from 5-13, older joints with 10-20, rarely, 

 however, increasing in numbers after the second year, 

 reddish brown, with inconspicuous, close-fitting sheaths, 

 % in. or less long: fls. bronze-colored, 1-1% in. wide: 

 fr. pyriform to clavate, of same color as joints, never 

 yellow, sometimes tinged with red or purple, unarmed 

 or with a few persistent short spines, 1-2 in. long. 

 Ariz., northern Mex. 



58. tetracantha, Tourney. An irregularly branching 

 shrub, 2-5 ft. high, primary branches from a stout, up- 

 right trunk 2-4 in. in diam., and bearing numerous 

 short lateral ones at irregular intervals : joints very 

 variable in length, usually 4-10 in. long and % in. thick: 

 areolse with whitish wool and a crescent-shaped tuft of 

 light brown bristles; spines 4, rarely more or less, %- 

 1% in. long, stout, loosely sheathed, straw-colored, 

 flattened, strongly deflexed, not increasing in numbers 

 on older joints : fls. greenish purple, %-l in. broad : fr. 

 obovate to subglobose, %-l in. long, juicy, scarlet, un- 

 armed, or with a few stiff deflexed spines. Arizona. 

 One of the most attractive of the cylindrical Opuntias 

 on account of its numerous bright scarlet fruits. 



59. arbuscula, Engelm. A short, numerously branched, 

 round-headed, arborescent plant, rarely reaching the 



1549. Opuntia ramosissima. No. 61. 



height of 5 ft., but always with an upright, well-defined 

 trunk, having rough, brown, unarmed bark: joints usu- 

 ally 2-4 in. long and % in. wide, easily broken from the 

 plant: areolae comparatively large, with white wool and 

 brush-like tufts of long, slender, yellow bristles: spines 

 yellow, usually 1, frequently a small, slender, additional 

 one at either side, %-!% in. long, loosely sheathed: 

 bronze-colored, %-l in. wide: fr. unarmed, of same color 



