OPUNTIA 



in (liam., having a thick, i-ivi' !i, -rn!-,-, i;ii-irmp(l hark: 

 joints congested towaril til' — .[i, ! . i inches, 



ovate to ovate-cylindri.al, . : h J in. 



thiols, very fragile and tin I. i. . : i_ ;> uiched 



and talcing root, bluish fc . i;. -■ iii< ^^ li:ii ^Im. -u- : m-eo- 

 lie with white wool and In-iglit stniw-colured bristles; 

 spines on young growth 5-8, increasing yearly until 

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

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

 tls. %-l in. witle, pink : tr. oi^ovate 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. mamill&ta, C'oult. 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: lis. greenish red, 1 in. broad: fr. 

 very spiny, ovate, 1 '4-2 in. long and one-third as wide, 

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



53. imbric4ta, 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 U in. long and 1-lJi in. thick, 

 with very prominent long, cristate tubercles : areolse 

 with yellowish wool and straw-colored bristles; spines 

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



OPUNTIA 



1151 



sheathed, whit< 

 light purple: fr 

 tubercles, yelb. 

 plant and dryin 

 and northern M 

 cens, from win- 



-colored: fls. 2-2}^ in. wide, 



diprcssed globose, with large 



II Ml .liam., adhering to the 



I luring the winter. Tex. 



"iii'used with O. arhoreK- 



II 11-. smaller growth, differ- 



>iin>. iitrger, more prominent 



js. The fruit and flower also 



low, frequently remaining on the stems during the sec- 

 ond year. Ariz., northern Mex. 



5(i. Whipplei, Engelm. and Bigel. A spreading, sub- 

 prostrato shrub, rarely o\.'efdiiig 2 ft, in hiislit, with 



desc 



iptiou. 



57. versicolor, Engelm. A small, numerously branched 

 tree, G-10 ft, hitrh, with rounded head and asliort trunk, 



liaviii- Ml til, lifiht brown or reddish brown, unarmed 



lirirk : inintv iimrh elongated, usually 0-12 in, long, some- 

 tiin.- I'll, I ill, thick, deep green, more or less colored 



however, increasinu 1 1 i .1 .11 1 ,. . : 1 ;tr, 



reddish brown, wit 1 1 1, I . 1,1 lis. 



tetracantha, Toumey. 



tubercles, an. I I. «. I 

 show markiil clill.r.iic-i-s, 



54, a^bore3cen8,l■:n^.•l•lm.(<^,.s■^■//(?^r7,Salm.). An arbor- 

 escent, numerously-brarM-lMil ilmf. I s ft, high, with 

 trunk of larger plants liaNi'- lIi .lark, unarmed 

 bark: joints with model;.!. narrow, cristate 

 tubercles, verticillate. b.. I ...lingon mostly 

 pendulous, moderately s|, hn 1,. n , i , in..stly ,V(i in. 

 long and 1 in. or less tliiek: ar...l..' \\ \\\\ .liily wliii.- 

 wool and small yellow to light bi'..un l.ri-tl.^: -|.iii.- 

 G-20, variable in length, 1 in. or bs., .■.niial ..n.- iii..r.' 

 loosely sheathed, horny or reibli^h I....\mi. wlnt.- t.i 

 straw-colored sheaths:' tls, piii| I. . ' > i.l.: fr, 

 unarmed or with few spines, CI. n~|: i.ubite, 

 subglobosc, 1 in, in diam,, yill. I. red. 

 Southwest U. S. — Frequently cnm .1 ,1:11 " imhri- 

 cafa and O. s;);»o,.;io)-, internu-diaie l..-iueeii ibe two. 

 Differs from the latter in having much larger, more 

 cristate tubercles, fewer spines and different fruit. 



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

 with numerous verticilhitr hranebes. farming a rounded 

 head, the cylindrical trunk n~nally branching a few 

 feet above the ground, an. I will. r..iiL'ti. dark brown or 

 grayish unarmed bark : j.iinis v . m. illat. and pendulous, 

 ultimate ones usually 4-S in, l.iit; 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, variouslv 

 colored bristles; spines ll)-:!(i." iiiereasing in number ally 2^ in 



yearly as the .i.'iiii - 1" i-i l-i. run"; linilh 'I. .Hiuniis. plant: ar. 



short, and ran 1 . ' ■■-% brush-lik. 



in. long: fls, ^1.. 1 1. i r , 1 . _". in. yellow, u - 



wide, in whorls at ■ 1,1 .ni ..in.i nii ir . 1 1 m i i.-al to oneateiti 



irregularly branching 

 ches from a stout, up- 

 nd bearing numerous 

 iitervals : joints very 

 . I.ing and }4 in. thick: 

 . -.ent-shaped tuft of 

 1. ly more or less, %- 

 . iiibed, straw-colored. 



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

 round-headed, arborescent plant, rarely reaching the 



Ife^- 



isily broken from the 

 \Mth white wool and 

 II .n bristles: .spines 



II slender, additional 



1 .sely sheathed: fls. 



..tnned. of same color 



