STANDLEY TREES AND SHRUBS OF MEXICO. 873 



with, closely set areoles and almost impenetrable armament ; tubercles slightly 

 elevated, pale green, somewhat 4-sided, about as long as broad, 1 cm. broad 

 or less ; spines, as well as their papery sheaths, pale yellow ; flowers several, 

 borne at the tips of the branches, 4 cm. long (including the ovary) ; sepals 

 orbicular, about 1 cm. in diameter, tinged with red ; petals 1.5 cm. long, pale 

 magenta to crimson; ovary 2 cm. long, its large areoles bearing brown wool 

 and several acicular spines; fruit usually naked, strongly tuberculate, the 

 upper tubercles larger than the lower. 



For an illustration of this species see Contr. U. S. Nat. Herb. 16: pi. 128, B. 



11. Opuntia ciribe Engelm. ; Coulter, Contr. U. S. Nat. Herb. 3: 445. 1896. 

 Central Baja California. 



One meter high or less, with numerous stout branches, densely armed ; 

 ultimate joints 4 to 5 cm. in diameter, strongly and regularly tuberculate, 

 3 cm. in diameter; tubercles about as long as broad (5 to 7 cm. broad) ; larger 

 spines 4 to 6, stout, 2 to 3 cm. long, covered with loose yellow sheaths, ac- 

 companied by several bristle-like spines or hairs ; glochids numerous ; flowers 

 yellow ; ovary somewhat bristly ; fruit strongly tuberculate, 3 to 4 cm. long, 

 spineless. 



12. Opuntia cholla Weber, Bull. Mus. Hist. Nat. 1: 320. 1895. 

 Widely distributed in Baja California. 



Usually treelike, 1 to 3 meters high, with a definite trunk 7 to 15 cm. in 

 diameter ; trunk very spiny at first and becoming more spiny each year for 

 some time, but in age spineless and developing a smooth, brownish yellow 

 bark ; top of plant often dense and broad ; joints often in whorls, horizontal, 

 pale, with large compressed tubercles ; spines usually numerous, more or less 

 porrect, covered with loose brownish sheaths; glochids numerous, yellow; 

 flowers rather small, 3 cm. broad, deep purple; fruit often 4 to 5 cm. long, 

 usually proliferous, often in long chains of 8 to 12 individuals or forming 

 compound clusters ; seeds numerous, very small, often abortive. "Cholla." 



In this as in some other species the fruits are proliferous, hanging on for 

 a few years and usually remaining green. They are, however, easily detached, 

 and on falling to the ground take root and form new colonies. For an illus- 

 tration of O. cholla see Contr. U. S. Nat. Herb. 16: pi. 128, A. 



13. Opuntia calmalliana Coulter, Contr. U. S. Nat. Herb. 3: 453. 1896. 

 Baja California, the type from CalmalM. 



Habit and height unknown ; joints cylindric, 1 to 2 cm. in diameter, glau- 

 cous, with linear-oblong crested (mostly distinct) tubercles 20 to 25 mm. long; 

 pulvini densely covered with yellowish wool, and with a penicillate tuft of 

 whitish bristles at upper edge; spines usually 4, the upper one stout and por- 

 rect, reddish with yellowish tip, 2 to 2.5 cm. long (occasionally 1 to 2 short 

 upper ones added), the usually 3 (sometimes 4) lower ones more slender and 

 sharply deflexed, 1 to 1.5 cm. long (occasionally one of them longer) ; flowers 

 apparently purple ; ovary covered with very prominent woolly pulvini, ripen- 

 ing into a smooth juicy obovate fruit ; seeds discoid and beaked, irregularly 

 angular, with broad commissure, about 4 mm. broad. 



14. Opuntia versicolor Engelm.; Coulter, Contr. U. S. Nat. Herb. 3: 452. 1890. 

 Sonora. Arizona, the type from Tucson. 



Bushy or treelike, 2 to 4 meters high, with a large open top sometimesi 5 

 meters broad ; trunk and larger stems woody throughout ; terminal joints 10 

 to 20 cm. long, 2.5 cm. in diameter, variously colored, not strongly tuberculate 

 when living; tubercles 1.5 cm. long; spines 5 to 11, 5 to 25 mm. long, dark- 

 colored, with close-fitting sheaths ; glochids reddish brown ; flowers variously 



