540 CACTACEAE 



The plants are usually gregarious, often extensively so (cf. fig. 250). The fallen joints 

 readily take root, a single plant becoming the parent of a continually enlarging group, and as 

 the joints adhere by their strongly barbed spines to passing animals, or are rolled along by the 

 wind, they are carried to a distance, and may thus become the propagators of new colonies. Not- 

 withstanding the formidable armament of the joints these plants are collected by pack rats, who 

 heap them up in groat piles for the protection of their nests. 



Locs. — Mountain Sprs., Mearns 3153; betw. County Well and Indio, Jepson 6033; White- 

 water, Parish. 



Kefs. — Opuntia bigelovii Engelm. Proc. Am. Acad. 3:307 (1856), type loc. Bill Williams 

 River, w. Ariz., Bigclow ; Pac. E. Rep. 4:50, pi. 19 (1856) ; Parish in Jepson, Man. 655 (1925). 



3. 0. prolifera Engelm. Coast Ciiolla. Steins several, stout, erect, 3 to 6 

 feet high, with numerous spreading branches, the tumid ultimate joints 3 to 6 inches 

 long, readily disarticulating; tubercles short, each with 6 to 10 spines i/o to 1 inch 

 long, their loose sheaths rusty-yellow ; flowers red ; fruit sub-globose, 1 inch long, 

 spineless or nearlj^ so, usually infertile, proliferous. 



Arid hillsides near the coast, 5 to 500 feet : Los Angeles Co. to San Diego Co. 

 South to Lower California. The species forms dense thickets and is propagated 

 almost entirely by the deciduous joints. Apr.-May. 



Locs.— San Pedro (Bull. N. Y. Bot. Gard. 6:422) ; Santa Catalina Isl. (Proc. S. Cal. Acad, 

 1:11) ; Ne\j-port, L. M. Booth; San Diego, Abrams. 



Refs. — Opuntia prolifera Engelm. Am. Jour. Sci. ser. 2, 14:338 (1852), tj-pe loc. San 

 Diego, Parry; Parish in Jepson, Man. 655 (1925). 



4. 0. acanthocarpa Engelm. & Bigel. Buckhorn Cholla. Erect, 2 to 6 feet 

 high, the stout stems few, with numerous ascending branches ; tubercles promi- 

 nent, elongated and laterally flattened, each bearing 8 to 25 spines; spines un- 

 equal, yellow, 1 inch long or less, their sheaths whitish or yellow ; flowers reddish ; 

 fruit dry, armed with buuches of 10 to 12 stoutish spines ; seeds more or less angled, 

 their margins channeled. 



Arid hills, 200 to 5000 feet : eastern Mohave Desert. East to and more abundant 

 in Nevada, Arizona and Sonora. Usually gregarious ; infrequent. May. 



Locs. — Bonanza King Mine, Mum, Johnston 4" Earwood 4299; Leastalk, Parish; Barnwell, 

 Jepson 5621 ; Whipple Mts., Colorado River, Jepson 5230. 



Refs. — Opuntia acanthocarpa Engelm. & Bigel. Proc. Am. Acad. 3:308 (1856), type loc. 

 Cactus Pass, 500 mi. w. of Santa Fe, Bigelow; Pac. R. Rep. 4:51, pi. 18, figs. 1-3 (1856); 

 Parish in Jepson, Man. 655 (1925). 



5. 0. parryi Engelm. Valley Cholla. Stems few, erect, 2 to 4 feet high, 

 branches upwardly-spreading; joints 6 to 12 inches long; tubercles prominent, % 

 inch long; areoles oblong, l^ inch long, bearing abundant white wool and 1 to 3 

 unequal acicular spines (these yellow, becoming brown in age, % to 1 inch long, 

 deflexed or porrect) and 4 to 7 shorter ones; flowers numerous, clustered about 

 the ends of the older stems, yellowish, tinged with red, % inch long ; fruit broadly 

 obovate, % to 1 inch long, with 3 to 4 rows of prominent tubercles, the upper ones 

 each bearing a single acicular spine i/^ to I/4 inch long ; seeds 1 to several, their 

 margins channeled. 



Arid gravelly benches, 900 to 2400 feet : San Bernardino Valley and its borders ; 

 San Diego Co. Apr.-May. 



Abundant but scattered and not forming close thickets. The fruit remains green and adher- 

 ent to the joints for at least a year, at last becoming dry and falling off. 



Locs. — Banning, Tourney; Riverside, Beed; San Bernardino, Parish; Upland, Johnston; 

 Pala (Britt. & Rose, Cactaceae 1:57). 



Refs.— Opuntia parryi Engelm. Am. Jour. Sci. ser. 2, 14:339 (1852), type loc. San Felipe, 

 e. San Diego Co., Parry; Pac. R. Rep. 4:48, pi. 22, figs. 4-7 (1856) ; Britt. & Rose, Cact. 1:57 

 (1919) ; Parish in Jepson, Man. 655 (1925). 0. bernardina Engelm.; Parish, Bull. Torr. Club 

 19:92 (1892), type loc. San Bernardino Valley, Parish. 



6. 0. echinocarpa Engelm. & Bigel. Summer Cholla. Erect, assurgent or 

 declined, either 1 to few-stemmed and loosely few-branched, or with few ascending 



