690 



TREES OF NORTH AMERICA 



and short light brown bristles, their spines 5-15 on the tubercles of young joints 

 and 30-50 on those of older branches, and slender, white to light reddish brown, 

 closely invested in white glistening sheaths, stellate-spreading, ^'-f long, those 

 in the interior sometimes considerably longer than the radial spines. Bark of 

 the trunk and of the larger limbs about \' thick, spineless, nearly black, broken 

 into elongated ridges, and finally much roughened by numerous closely appressed 

 scales. Wood light, soft, pale reddish brown, and conspicuously reticulate, with 

 conspicuous medullary rays and well defined layers of annual growth; sometimes 

 used in the manufacture of light furniture, canes, picture-frames, and other small 

 articles. 



Distribution. Widely scattered over the mesas of southern Arizona south of the I 

 Colorado plateau and over the adjacent regions of Sonora. 



3. Opuntia versicolor, Coult. 



Leaves terete, abruptly narrowed to the spinescent apex, ^'-^' long, persistent 

 on the branches four to six weeks. FloAvers opening in May, about 1^' in diameter. 



fK J6i 



with ovaries I' long, broadly ovate acute sepals, and narrow obovate petals rounded 

 above and green tinged writh red or with yellow. Fruit usually clavate, 2'-2^' lowg> 

 nearly 11' in diameter, with areolae generally only above the middle and usually 

 furnished with 1-3 slender reflexed persistent spines about ^' long, or occasionally 

 spineless, rarely nearly spherical and only about f in diameter, ripening from De- 

 cember to February, and at maturity the same color as the joints on which it grows, 

 usually withering, drying, and splitting open on the tree, or remaining fleshy and 

 persistent on the branches until the end of the following summer, and sometimes 

 through a second winter, or often becoming imbedded in the end of a more or less 

 elongated joint; seeds irregularly angled, with narrow commissures. 



A tree, with an erect trunk occasionally 6-8 high and 8' in diameter, numerous 

 stout irregularly spreading often upright branches, and cylindrical terminal joints 

 generally 6'-12' but sometimes 2 in length, f '-1' in diameter, covered with a thick 

 dark green or purple epidermis, marked by linear flattened tubercles, their woody 

 skeletons usually formed during their second season. Areolae large, oval, clothed 

 with gray wool, generally bearing a cluster of small bristles, and slender stellate- 

 spreading brown or reddish brown spines, with close early deciduous straw-colored 



