Silver Cholla or Gold Cholla, depending on color of the spines (Opuntia echinocarpa)

Cholla cactus represent more than 20 species of the Opuntia genus (Family Cactacea) in the North American deserts. Cholla is a term applied to various shrubby cacti of this genus with cylindrical stems composed of segmented joints. These stems are actually modified branches that serve several functions -- water storage, photosynthesis and flower production.