Prickly Pear

Description:

Prickly pears typically grow with flat, rounded cladodes (also called platyclades) armed with two kinds of spines; large, smooth, fixed spines and small, hairlike prickles called glochids, that easily penetrate skin and detach from the plant. — Wikipedia

Habitat:

Prickly pear cactus are found in all of the deserts of the American Southwest, with different species having adapted to different locale and elevation ranges. Most require course, well-drained soil in dry, rocky flats or slopes. But some prefer mountain pinyon/juniper forests, while others require steep, rocky slopes in mountain foothills. — desertusa.com

Notes:

Charles Darwin was the first to note that these cacti have thigmotactic anthers: when the anthers are touched, they curl over, depositing their pollen. This movement can be seen by gently poking the anthers of an open Opuntia flower. The same trait has evolved convergently in other cacti (e.g. Lophophore). — Wikipedia