The cactus is one of the most recognizable plants native to the Americas. The thick, fleshy stems of cacti rarely exhibit leaves and instead typically bear numerous prominent spines, which offer them protection from a wide range of animals. Most cacti thrive in the desert, where several adaptations enable them to acquire and retain as much water as possible from the environment. The shallow root system characteristic of cacti allows enhanced uptake of water following the gentle rain showers that sometimes occur in the arid habitats they commonly populate. Also, without leaves, cacti lose a much smaller amount of water via transpiration than do most other plants. A tough layer of tissue surrounding the stems of cacti and special substances within the storage cells located inside the stems further reduce loss of water.