This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Prostrate, similar to the preceding specie;;; joints obovate to suborbicular, or oval, usually deep green, 2'-5' long; leaves subulate, spreading, 3'-5" long; bristles reddish brown; spines few, mostly near the margins of the joints, 1-4 together, whitish, or reddish at base and apex, deflexed, or the longer one spreading and 1/2-l long; flowers yellow, often with a reddish centre, 2 1/2'-3 1/2' broad; petals 10-12; fruit club-shaped, not spiny, fleshy, edible, 1 1/2-2' long.
Opuntia macrorhiza Engelm., a related species with a deep woody root, abundant in Texas, is reported to range northward into Missouri and Kansas.
Opuntia tortispina Engelm. Pac. R. R. Rep.
4: 31. 1856.
Stems prostrate, the orbicular-obovate flattened joints 6-8' long. Spines 3-5, yellowish, becoming whitish, angled and channeled, sometimes twisted, the longer ones 1 1/2'-2 1/2' long, with 2-4 more slender and shorter ones; flowers sulphur-yellow, 2V-3' broad; fruit ovoid, fleshy, unarmed, about 2' long and 1' in diameter; seeds orbicular, slightly notched at the hilum, 2"-3" wide.
Plains of Missouri and Nebraska to Texas. Summer.
Opuntia camanchica Engelm. Pac. R. R. Rep. 4: 40. 1856.
Prostrate, with obovate-orbicular flattened joints 6'-8' long, 5'-8' wide. Spines 1-3, flattened, reddish brown to blackish, 1 1/2-3' long, or with 3-6 additional shorter ones, the upper one suberect, the others deflexed or spreading; flowers yellow, about 2 1/2' broad; fruit oval, deep red, juicy, 1 1/2-2' long; seeds angular, margined, deeply notched at the hilum, 2"-3" broad.
Western Kansas (according to B. B. Smyth); Colorado to Texas and Arizona.
The plant of western Kansas differs from the typical Texan one by having more slender spines, lighter in color. It hybridizes with O. fragilis.
Opuntia missounensis DO Prodr. 3: 472. 1828.
Prostrate, joints broadly obovate to orbicular, tubercled, pale gree: , 2'-6' long, about 6" thick, the tubercles 2' high, densely spiny and with cushions of fine bristles; spines 5-12, slender, 6"-2' long, whitish; leaves minute; flowers light yellow, 2-3' broad; fruit dry, very prickly, 1'- 1 1/24' long.
Plains and dry soil, Wisconsin to South Dakota, Athabasca, British Columbia, Nebraska, Missouri, Utah and New Mexico. May-June.