Cacti and succulents
The cactus family has nearly 2000 species and with only one exception, they are native to America. They range from the Arctic Circle to the mountains of Chile, but are most abundant in the southwestern United States and Mexico.
The term succulent refers to a broad category of plants, including cacti which have developed think fleshy leaves or stems. These serve as water storage organs to insure survival under arid conditions. Succulents are found worldwide. Besides cacti, they include many familiar plants: Crassula aborescens (Jade plant) and Aloe barbadensis (Medicine plant).
Cacti can be tall and lanky or squat and spherical, frequently without any branches, and most always without leaves. These shapes result in a large proportion of internal tissue to external surface area which reduces the amount of moisture that is lost through the plant itself. They often have scales or spines ranging from microscopically small to wickedly large and barbed. These protect against predators and are thought to aid the plant in withstanding hot drying rays of the sun.