Distribution. Widely scattered over the mesas of southern Arizona south of the Colorado plateau and of the adjacent regions of Sonora.
3. [Opuntia versicolor] Coult.
Leaves terete, abruptly narrowed to the spinescent apex, ⅓′—½′ long, persistent on the branches from four to six weeks. Flowers opening in May, about 1½′ in diameter, with ovaries ⅝′ long, broad-ovate acute sepals, and narrow obovate petals rounded above and green tinged with red or with yellow. Fruit usually clavate, 2′—2½′ long, nearly 1½′ in diameter, with areolæ generally only above the middle and usually furnished with 1—3 slender reflexed persistent spines about ½′ long, or occasionally spineless, rarely nearly spherical and only about ¾′ in diameter, ripening from December to February, and at maturity the same color as the joint 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 or often upright branches, and cylindric terminal joints generally 6′—12′ but sometimes 2° in length, ¾′—1′ in diameter, and covered with a thick dark green or purple epidermis, marked by linear flattened tubercles, their woody skeletons usually formed during their second season. Areolæ 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 sheaths, 4—14 and on old tubercles 20—25 in number, the inner 1—4 in number, usually deflexed and unequal in length, the longest about ⅓′ long and longer than the radial spines. Bark of the trunk and of the large branches smooth, light brown or purple, usually unarmed, ½′—¾′ thick, finally separating into small closely appressed black scales. Wood reticulate, hard, compact, light reddish brown and rather lustrous, with thin conspicuous medullary rays, well-defined layers of annual growth, and thick pale or nearly white sapwood.
Distribution. Foothills and low mountain slopes of southern Arizona and northern Sonora; very abundant.
XLVI. RHIZOPHORACEÆ.
Glabrous trees or shrubs, with terete branchlets, and usually opposite coriaceous entire persistent leaves, with interpetiolar stipules. Flowers in axillary clusters; calyx-lobes valvate in the bud, persistent; petals inserted on the tube of the calyx and as many as its lobes; stamens inserted at the base of a conspicuous disk; anthers 2-celled, the cells opening longitudinally; pistil of 2—5 united carpels; ovary 2—5-celled; ovules usually 2 in each cell, suspended from its apex, collateral, anatropous; raphe ventral; micropyle superior. Fruit usually indehiscent, 1-celled and 1-seeded.
The Mangrove family is tropical, with most of its seventeen genera confined to the Old World.