6. Opuntia Fràgilis (Nutt.) Haw. Brittle Opuntia. Tuna

Fig. 2991

Cactus fragilis Nutt. Gen. 1: 296. 1818.

Opuntia fragilis Haw. Syn. Pl. Succ. Suppl. 82. 1819.

Decumbent or prostrate; joints ovoid, l'-2' long, somewhat flattened or nearly terete. Leaves very small, reddish; cushions composed of few bristles; central spines 1-4, 1/2'-1 1/2' long, gray, darker at the apex, surrounded by 4-6 smaller ones; flowers yellow, smaller than those of the preceding species; fruit nearly 1' long, becoming dry at maturity, provided with cushions of bristles usually bearing a few short spines.

Prairies and dry soil, Iowa, Wisconsin and Minnesota to South Dakota, British Columbia, Kansas and Utah. July-Sept.

7. Opuntia Arboréscens Engelm. Tree-Cactus

Fig. 2992

Opuntia arborescens Engelm. Wisliz. Rep. 6. 1848.

Erect, tree-like, 4°-25° high, 4'-8' in diameter at the base, verticillately branched, the spiny branches spreading or drooping. Joints verticillate, mostly in 3's or 4's, cylindric, 2'-6' long, less than 1' in diameter, the prominent tubercles 7"-10" long; leaves terete, spreading, 6"-10" long; spines 8-30, terete, in yellowish sheaths, diverging, the interior ones the longer, often 1' long or more; flowers purple, 2 1/2-3' broad; fruit subglobose, crested-tuberculate, dry, or nearly so, yellow, unarmed, about 1' in diameter; seeds smooth, 1 1/2-2" wide.

Western Kansas, probably only in cultivation; Colorado to Texas, New Mexico, Arizona and Mexico.

Vou II.