CACTUS FAMILY 539 



Ultimate joints readily disarticulating; fruit proliferous, spineless or nearly so. 



Tubercles nearly quadrangular; spines whitish, shining; deserts 2. 0. bigelovii. 



Tubercles longer than wide; spines dull yellow; coastal 3. 0. prolifera. 



Joints firmly attached ; tubercles prominent, elongated. 

 Tubercles 2 to 3 times as long as wide. 



Fruit-spines stoutish, in bundles of 8 to 12 ; deserts 4. 0. acanthocarpa. 



Fruit-spines acicular, solitary or few; interior 5. O.parryi. 



Tubercles less than twice as long as wide. 



Tubercles ovate ; principal spines 3 or 4 ; deserts 6. 0. echinocarpa. 



Tubercles flattish; principal spines 7 to 20; coastal 7. 0. serpentina. 



Spines roughened, gray, sheathless; woody axis wanting or rudimentary; deserts 8. 0. parishii. 



B. Joints flattened (that is, phylloclades), not tuberculate. — Subgenus Platyopuntia. 



Fruit dry. 



Fruit spineless, or nearly so 9. 0. hasilaris. 



Fruit spiny. 



Joints somewhat turgid; areoles white-woolly 10. 0. fragilis. 



Joints flat and thin. 



Areoles approximate; spines acicular or bristle-like 11. 0. erinacea, 



Areoles distant; spines subulate 12. 0. rhodantha. 



Fruit fleshy or juicy. 



Arboreous, with definite trunk ; or large shrubs with upwardly spreading branches, and large 

 and thick joints. 

 Spines wanting or few, if present whitish or brown ; introduced species ; coastal. 



Fruit yellow or reddish, fleshy; umbilicus flat 13. 0. megacantha. 



Fruit purple, juicy; umbilicus depressed 14. 0. ficus-indica. 



Spines abundant, yellow; fruit purple; deserts 15. 0. chlorotica. 



Shrubby, much branched from the base ; spiny. 

 Joints 6 to 12 inches long ; flowers yellow. 



Stems erect or ascending; cismontane S. Cal 16. 0. occidentalis. 



Stems declined or assurgent; deserts 17. 0. mohavensis. 



Joints 3 to 6 inches long; stems prostrate or assurgent; cismontane 18. 0. vaseyi. 



1. 0. ramosissima Engelm. Pencil Cactus. Bush 1 to 6 feet high, the stems 

 erect, few, rarely numerous, when mature gray and very woody, usually sparsely 

 spiny above, rarely throughout, sometimes spineless ; branches numerous, slender, 

 cylindrical ; tubercles tessellate, 4 to 6-angled ; areoles grooved, bearing a single 

 upwardly spreading stout spine 1 to l^/^ inches long, its yellow sheath loose and 

 shining, and below it a deflexed spine % inch long ; flowers i/^ inch long, purplish ; 

 fruit dry, densely clothed with slender tawny spines. 



Dry washes or gravelly benches, 450 to 3500 feet : Colorado Desert ; eastern 

 Mohave Desert. East to Nevada and Arizona, south to Mexico. Apr.-May. 



Frequent, the individuals solitary or distant, never gregarious. The areoles of the spinifer- 

 ous forms contain wool and glochids, both abundant, but in the spineless forms both are sparse 

 or even wanting. 



Locs. — San Felipe Narrows, e. San Diego Co., Jepson 8795; Palm Sprs. of San Jacinto, 

 Parish; Warrens "Well, Jepson 5963 ; Quail Spr., Muns 5297 ; Cottonwood Spr., n. of Mecca, Jep- 

 son 12,622a; Eiverside Mts., Colorado Kiver, Jepson 524:7 ; Needles, Parish; Leastalk, Parish. 



Eefs. — Opuntia ramosissima Engelm. Am. Jour. Sci. ser. 2, 14:339 (1852), type loc. near 

 the lower Colorado Eiver, Parry; Parish in Jepson, Man. 655 (1925). 0. tessellata Engelm. Proc. 

 Am. Acad. 3:309 (1856), "valley of the lower Colorado [Eiver], from Sonora to the California 

 mountains;" Pac. E. Eep. 4:52, pis. 21 and 24, fig. 20 (1856). 



2. 0. bigelovii Engelm. Jumping Cholla. Erect, 2 to 4 feet high, the usually 

 single stem upwardly branched above, forming a close head ; joints short, turgid, 

 the ultimate readily detached, the primary strongly adhering, the lowest hanging 

 dead and blackened about the stem ; tubercles quadrangular, elevated, concealed 

 by the abundant divergent spines, these 1 to li/4 inches long, yellowish and glisten- 

 ing; flowers in clusters at the apex of the joints, greenish-yellow, 1 to 1% inches 

 long ; fruit dry, spineless or nearly so, 1 inch long, few-seeded, usually infertile. 



Dry hillsides or benches, -75 to 1130 feet : Colorado Desert. East to south- 

 western Nevada and to Arizona, south to Lower California. Apr. 



