CACTUS FAMILY 541 



stems and numerous spreading branches forming a compact bush 3 to 5 feet high 

 (var. robustior) ; joints 3 to 6 inches long; tubercles short, ovate, each armed with 

 3 or 4 stout yellowish spines, I/2 to 1 inch long, and 8 to 10 shorter ones ; flowers 

 clustered, yellowish, tinged with red ; fruit dry, the upper areoles bearing bundles 

 of 8 to 12 spines i/4 to % inch long, usually unarmed below the middle; seeds 

 numerous, their margins stronglj' channeled. 



Desert areas, 1800 to 2800 feet : Colorado and Mohave deserts. East to Utah, 

 south to Lower California. Apr.-June. 



Common but solitary, or sometimes forming open groves, but never in close thickets. As 

 here interpreted the species includes forms diverse in habit, but without satisfactory technical 

 difference to permit segregation. 



Locs. — Cabezon, Parish 648 (var. robustior) ; Pinon Wells, Mum 4487; Eock Creek, Airams 

 4- McGregor 564 ; Ivanpah, Parish. 



Eefs. — Opuntia echinocarpa Engelm. & Bigel. Proc. Am. Acad. 3:305 (1856), type loe. 

 "valley of the lower Colorado River", that is, near mouth of Bill "Williams River, Ariz., Bigelow; 

 Pac. R. Rep. 4:49, pi. 18, figs. 5-10 (1856) ; Parish in Jepson, Man. 656 (1925). 0. echinocarpa 

 var. rohustior Coult. Contrib. U. S. Nat. Herb. 3:446 (1896). 0. echinocarpa var. parkeri Coult. 

 I.e., type loc. San Diego Co., e. side of the mountains, facing the desert, C. F. Parlcer. 



7. 0. serpentina Engelm. San Diego Cholla. Stems declined or assurgent; 

 branches divaricate, ascending, elongated-cylindrical, not tumid, 6 to 12 inches 

 long; tubercles prominent, short and flattish, each bearing 7 to 20 acicular yellow- 

 ish spines i/4 to % inches long; flowers greenish-yellow, tinged with red, mostly 

 1 inch high; fruit broadly ovoid, deeply umbilicate, very spiny. 



Dry coastal hills, 5 to 500 feet : San Diego. South to Lower California. 



Refs. — Opuntia serpentina Engelm. Am. Jour. Sci. ser. 2, 14:338 (1852), type loc. dry 

 hillsides, San Diego, Parry; Parish in Jepson, Man. 656 (1925). 0. calif ornica Gov. Proc. Biol. 

 Soc. Wash. 13:119 (1899). (l)Cereus californicus T. & G. Fl. 1:555 (1840), type loc. "arid 

 hills and denuded tracts near St. Diego, California, common," Nuttall. 



8. 0. parishii Orcutt. Mat Cholla. Stems prostrate, rooting along the lower 

 surface; brancheiB approximate, simple or 1 to 2-branched, erect, 3 to 5 inches 

 high; tubercles prominent, elongated, 14 inch high; areoles circular, filled with 

 white wool; glochids yellow, scanty; spines all sheathless and nearly destitute of 

 barbs, roughened, the central 3 or 4 divergent, stout, flattened, ashy-gray, the 

 lowest longest and broadest, 1 to 2 inches long, the secondary 6 to 12 acicular, un- 

 equal; flowers yellow; fruit dry, ovate, 2 inches long, the deep umbilicus filled 

 with the withered floral segments, the areoles large, filled with cushions of white 

 wool, bordered by abundant yellow glochids, these ^4 inch long, radiate and com- 

 pletely concealing the surface; seeds numerous, yellowish-white, about I/4 inch 

 wide. 



Loose sandy soil, 2500 to 3500 feet: eastern Mohave Desert; mountains on 

 north side of Colorado Desert ; infrequent. 



This species forms mats in which the stems are often buried. The spines and glochids appear 

 to the touch, and even under a lens, to be destitute of barbs, but with the microscope a few can 

 be detected near the tips. 



Locs. — Leastalk, Parish; Pinon Wells, Mum 4483; Iron Chief Mine, Jaeger. 



Refs. — Opuntia parishii Orcutt, West Am. Sci. 10:1 (1896), type loc. Mohave Desert, 

 Parish; Baxter, Cactus and Sue. Jour. 6:12 (1934). 0. clavata Parish; Jepson, Man. 656 (1925). 



9. 0. basilaris Engelm. & Bigel. Beaver-tail Tuna. Stems low and spread- 

 ing, 4 to 12 inches long, few-jointed; joints orbicular to obovate, rarely ligulate, 

 mostly obtuse, 3 to 8 inches long, glaucous, glabrous or sub-pubescent; areoles 

 approximate, filled with abundant brown glochids, spineless; flowers 2 to 2^/2 

 inches high, light purple to rose-purple; fruit dry, spineless; seeds about i/4 inch 

 broad, more or less angled, raphe prominent. 



Arid slopes and valleys, usually in sandy soil, 2500 to 7000 feet: Inyo Co.; 

 Mohave and Colorado deserts and their bordering montane slopes; occasional in 



