Cactus is a member of the plant family Cactaceae, within the order Caryophyllales. Here's a taste of Sikkim's best cactus collection! Many live in extremely dry environments, even being found in the Atacama Desert, one of the driest places on earth. Cacti show many adaptations to conserve water. Most species of cacti have lost true leaves, retaining only spines, which are highly modified leaves. As well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. Cactus spines are produced from specialized structures called areoles, a kind of highly reduced branch. Areoles are an identifying feature of cacti. As well as spines, areoles give rise to flowers, which are usually tubular and multi-petaled. Like other succulent plants, most cacti employ a special mechanism called "Crassulacean acid metabolism" (CAM) as part of photosynthesis. Transpiration, during which carbon dioxide enters the plant and water escapes, does not take place during the day at the same time as photosynthesis, but instead occurs at night. The plant stores the carbon dioxide it takes in as malic acid, retaining it until daylight returns and only then using it in photosynthesis. Because transpiration takes place during the cooler, more humid night hours, water loss is significantly reduced. A few species differ significantly in appearance from most of the family. At least superficially, plants of the genus Pereskia resemble other trees and shrubs that grow around them. They have persistent leaves, and when older, bark-covered stems. Their areoles identify them as cacti, and in spite of their appearance they too have many adaptations for water conservation. Pereskia is considered close to the ancestral species that all cacti evolved from. In tropical regions, other cacti grow as forest climbers and epiphytes (plants that grow on trees). Their stems are typically flattened, almost leaf-like in appearance, with fewer or even no spines, like the well known Christmas cactus or Thanksgiving cactus (in the genus Schlumbergera). Cacti have a variety of uses: many species are used as ornamental plants; others are grown for fodder or forage, others for food (particularly their fruit). Cochineal is the product of an insect that lives on some cacti. Sikkim is a landlocked Indian state located in the Himalayan mountains. The state borders Nepal to the west, China's Tibet Autonomous Region to the north and east, and Bhutan to the southeast. The Indian state of West Bengal lies to the south. With around 607,000 inhabitants as of 2011, Sikkim is the least populous state in India and the second-smallest state after Goa in total area, covering approximately 7,096 km2 (2,740 sq mi). Sikkim is nonetheless geographically diverse due to its location in the Himalayas; the climate ranges from subtropical to high alpine, and Kangchenjunga, the world's third-highest peak, is located on Sikkim's border with Nepal.[6] Sikkim is a pop
