Cactus
Overview
A cactus is a member of the plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines. Many species are used for ornamental plants, and some are also grown for fodder, forage, fruits, cochineal
Cochineal
The cochineal is a scale insect in the suborder Sternorrhyncha, from which the crimson-colour dye carmine is derived. A primarily sessile parasite native to tropical and subtropical South America and Mexico, this insect lives on cacti from the genus Opuntia, feeding on plant moisture and...

, and other uses.

Cacti come in a wide range of shapes and sizes.
Encyclopedia
A cactus is a member of the plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines. Many species are used for ornamental plants, and some are also grown for fodder, forage, fruits, cochineal
Cochineal
The cochineal is a scale insect in the suborder Sternorrhyncha, from which the crimson-colour dye carmine is derived. A primarily sessile parasite native to tropical and subtropical South America and Mexico, this insect lives on cacti from the genus Opuntia, feeding on plant moisture and...

, and other uses.

Cacti come in a wide range of shapes and sizes. The tallest is Pachycereus pringlei
Pachycereus pringlei
Pachycereus pringlei is a species of cactus that is native to northwestern Mexico in the states of Baja California, Baja California Sur, and Sonora...

, with a maximum recorded height of 19.2 m, and the smallest is Blossfeldia liliputiana, only about 1 cm in diameter at maturity. Cactus flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s are large, and like the spines arise from distinctive features called areole
Areole
Areoles are an important diagnostic feature of cacti, and identify them as a family distinct from other succulent plants. The areoles on cacti are clearly visible; they generally appear as small light- to dark-colored bumps, out of which grow clusters of spines...

s.

Distribution

The cactus family is native to the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

, where their range extends from Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...

 to southern Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, but they are densest and most diverse in the regions of northern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 and the southern tropics
Tropic of Cancer
The Tropic of Cancer, also referred to as the Northern tropic, is the circle of latitude on the Earth that marks the most northerly position at which the Sun may appear directly overhead at its zenith...

 of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 and Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

. Rhipsalis baccifera
Rhipsalis baccifera
Rhipsalis baccifera, commonly known as the Mistletoe Cactus, is an epiphytic cactus which originates from Central and South America, the Caribbean and Florida. It is also spread throughout the tropics of Africa and Asia. This is the only cactus species naturally occurring outside the New World,...

is the one exception; it is native to both the Americas and the Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....

, where it is found in tropical Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

, and Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

. It is thought to have colonized the Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....

 within the last few thousand years, probably by being carried as seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s in the digestive tracts of migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...

 bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s. Many other species have become naturalized outside the Americas after having been introduced by people, especially in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, and the Mediterranean region. Cacti inhabit diverse regions, from coastal plains to high mountain areas.

Adaptations to dry environment

With a few exceptions, cacti are succulent plants and, like other succulents, they have a variety of adaptations that enable them to survive in hot and dry environments.

In most species of cacti the leaves have evolved into spines
Thorns, spines, and prickles
In botanical morphology, thorns, spines, and prickles are hard structures with sharp, or at least pointed, ends. In spite of this common feature, they differ in their growth and development on the plant; they are modified versions of different plant organs, stems, stipules, leaf veins, or hairs...

 which are capable of absorbing air moisture but have a very low ability to lose it. They also trap some moisture in a layer near to the cactus surface, reducing the water potential gradient. (Transpiration
Transpiration
Transpiration is a process similar to evaporation. It is a part of the water cycle, and it is the loss of water vapor from parts of plants , especially in leaves but also in stems, flowers and roots. Leaf surfaces are dotted with openings which are collectively called stomata, and in most plants...

 is reduced.) They also defend the cactus against herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s but also provide shade that lowers the plant's water loss through transpiration
Transpiration
Transpiration is a process similar to evaporation. It is a part of the water cycle, and it is the loss of water vapor from parts of plants , especially in leaves but also in stems, flowers and roots. Leaf surfaces are dotted with openings which are collectively called stomata, and in most plants...

. The spines grow from specialized structures called areole
Areole
Areoles are an important diagnostic feature of cacti, and identify them as a family distinct from other succulent plants. The areoles on cacti are clearly visible; they generally appear as small light- to dark-colored bumps, out of which grow clusters of spines...

s, homologous to the nodes on other plants. Very few members of the family have leaves, and when present these are usually rudimentary and soon fall off; they are typically awl-shaped and only 1–3 mm. long. Two genera, Pereskia
Pereskia
Pereskia is a genus of about 25 tropical species and varieties of cacti that do not look much like other types of cacti, having substantial leaves and thin stems. They originate from the region between Brazil and Mexico. The genus is named after Nicolas-Claude Fabri de Peiresc, a 16th century...

and Pereskiopsis
Pereskiopsis
Pereskiopsis is a genus of cacti .Peireskiopsis Vaupel is an orthographic variant.-Description:...

, do however retain large, non-succulent leaves 5–25 cm long, and non-succulent stems. Pereskia has now been determined to be the ancestral genus from which all other cacti evolved.
Enlarged stems
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

 carry out photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 and store water. Unlike other succulents, the stem is the only part of many cacti where this takes place. Cacti often have a waxy coating on their stems to prevent water loss and potentially repel water from their stems. Because of the plants' high water-retention ability, detached parts of the plant can survive for long periods and then grow new roots from anywhere on the plant body when rain comes.

The bodies of many cacti have become thickened during the course of evolution, and form water-retentive tissue that is in the optimal shape of a sphere or cylinder (combining highest possible volume with lowest possible surface area). By reducing its surface area, the body of the plant is also protected against excessive sunlight. The plant body itself is also capable of absorbing moisture (through the epidermis and the spines), which is especially important for plants that receive most of their moisture in the form of fog.

Most cacti have a short growing season
Growing season
In botany, horticulture, and agriculture the growing season is the period of each year when native plants and ornamental plants grow; and when crops can be grown....

 and long dormancy. For example, a fully-grown saguaro (Carnegiea gigantea) can absorb up to 3,000 liters of water in ten days. This is helped by the ability to form new roots quickly. Two hours after rain following a relatively long drought, root formation begins in response to the moisture. Apart from a few exceptions, an extensively ramified
Ramification (botany)
In botany, ramification is the divergence of the stem and limbs of a plant into smaller ones, i.e. trunk into branches, branches into increasingly smaller branches, etc. Gardeners stimulate the process of ramification through pruning, thereby making trees, shrubs and other plants bushier and...

 root system is formed, which spreads out beneath the surface. The salt concentration in the root cells is relatively high, so when moisture is encountered it is quickly absorbed.

Cacti often have very shallow roots that spread out widely close to the surface to collect water, an adaptation to infrequent rains. In one case, a young saguaro
Saguaro
The saguaro is a large, tree-sized cactus species in the monotypic genus Carnegiea. It is native to the Sonoran Desert in the U.S. state of Arizona, the Mexican state of Sonora, a small part of Baja California in the San Felipe Desert and an extremely small area of California, U.S...

 only 12 cm tall had a root system covering an area 2 m in diameter, but with no roots more than 10 cm deep. The larger columnar cacti also develop a taproot
Taproot
A taproot is an enlarged, somewhat straight to tapering plant root that grows vertically downward. It forms a center from which other roots sprout laterally.Plants with taproots are difficult to transplant...

, primarily for anchoring, but also to reach deeper water supplies and mineral nutrients.

Areole
Areole
Areoles are an important diagnostic feature of cacti, and identify them as a family distinct from other succulent plants. The areoles on cacti are clearly visible; they generally appear as small light- to dark-colored bumps, out of which grow clusters of spines...

s
are unique features to cacti. The areole appears like a cushion with a diameter of up to 15 mm, and is formed by two opposing buds in the angles of a leaf. The upper bud develops into either a blossom or a side shoot, while the lower bud develops into spines. The two buds of the areoles can lie very close together or be separated by several cm.

Like other types of succulents, cacti reduce water loss through transpiration by Crassulacean acid metabolism
Crassulacean acid metabolism
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. The stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide...

 (CAM). Here, transpiration does not take place during the day at the same time as photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

, but at night. The plant stores the carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, chemically linking it to malic acid
Malic acid
Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. It is a dicarboxylic acid which is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms , though only the L-isomer exists...

, until nighttime. Because transpiration takes place during the cooler, more humid night hours, water loss through transpiration is significantly reduced.

Cacti are one of a few species that are typically labeled Xerophytes, meaning they have adapted well to a particularly hostile environment.

Reproductive ecology

Some cactus flowers form long tubes (up to 30 cm) so only certain species of moths can reach the nectar, and therefore pollinate the blossoms. There are also specializations for species of bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s, hummingbird
Hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...

s and bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...

s. The duration of flowering is highly variable. Some flowers, such as those of Selenicereus grandiflorus
Selenicereus grandiflorus
Selenicereus grandiflorus is a cactus species originating from the Antilles, Mexico and Central America. The species is commonly referred to as Nightblooming Cereus, Queen of the Night , Large-flowered Cactus, Sweet-Scented Cactus or Vanilla Cactus. The true species is extremely rare in cultivation...

(Queen of the Night), are only fully open for two hours at night, while other species may flower for a whole week. Most cacti are self-incompatible
Self-incompatibility in plants
Self-incompatibility is a general name for several genetic mechanisms in angiosperms, which prevent self-fertilization and thus encourage outcrossing...

, and thus require a pollinator. A few are autogamous and are able to pollinate themselves. Frailea
Frailea
Frailea is a genus of globular to short cylindrical cacti native to Brazil. These species are cleistogamous. They were first classified in the genus Echinocactus....

s only open their flowers completely in exceptional circumstances; they mostly pollinate themselves or others with their flowers closed ("cleistogamy"). The flower itself has also undergone a further development: the ovary
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...

 tends to be highly protected by thorns, hairs and scales. Seed formation is prolific, and the fruits are mostly fleshy, pleasant tasting and conspicuously colored. Goats, birds, ants, mice and bats may contribute to seed dispersal.

History

Among the remains of the Aztec
Aztec
The Aztec people were certain ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica in the 14th, 15th and 16th centuries, a period referred to as the late post-classic period in Mesoamerican chronology.Aztec is the...

 civilization, cactus-like plants can be found in pictorial representations, sculpture and drawings, with many depictions resembling Echinocactus grusonii
Echinocactus grusonii
Echinocactus grusonii is a well known species of cactus native to central Mexico from San Luis Potosi to Hidalgo. Described by Heinrich Hildmann in 1891, it is popularly known as the Golden Barrel Cactus, Golden Ball or, amusingly, Mother-in-Law's Cushion...

. Tenochtitlan (the earlier name of Mexico City
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...

) means "place of the sacred cactus". The coat of arms of Mexico
Coat of arms of Mexico
The current coat of arms of Mexico has been an important symbol of Mexican politics and culture for centuries. The coat of arms depicts a Mexican Golden Eagle perched upon a prickly pear cactus devouring a snake. To the people of Tenochtitlan this would have strong religious connotations, but to...

 to this day shows an eagle perched on a cactus while holding a snake, an image which is at the center of the Aztec origin myth.

Christopher Columbus
Christopher Columbus
Christopher Columbus was an explorer, colonizer, and navigator, born in the Republic of Genoa, in northwestern Italy. Under the auspices of the Catholic Monarchs of Spain, he completed four voyages across the Atlantic Ocean that led to general European awareness of the American continents in the...

 brought the first melocactus
Melocactus
Melocactus is a genus of cactus with about 40 species. They are native to the Caribbean, northern South America, with some species along the Andes down to southern Peru, and a concentration of species in northeastern Brazil....

 to Europe.

Cultivation

With few exceptions, the vast majority of cacti in habitat almost always are found growing in mineral based soils. Epiphytic cacti are the exception and prefer soils rich in organic materials, however, cacti in this group which prefer these types of soils produce healthier plants when allowed to dry completely between waterings. Some species of cacti such as Toumaya papyracantha (formerly Pediocactus papyracantha -- found in the high mesas of New Mexico) are mycorrhiza
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....

l symbionts with the roots of various species of grasses and grow underground on the roots of these wild grasses, only emerging above ground and initiating photosynthesis for sexual reproduction and flowering, forming deciduous cactus bodies that die back in winter or during droughts.

The vast majority of commercial "cactus soil mixes" which contain organic materials are unsuitable for growing most terrestrial cacti, and many contain pumice, which exudes traces of heavy metals which will rot the roots of cacti if grown in these medium over a period of years. Surprisingly, most cacti prefer a mineral based soil cut with about half sand and allowed to dry out completely between waterings.

Although cacti are adapted to hot deserts and other xerophytic environments, most cacti evolved in mountainous areas and require moderate cold and/or cool night temperatures for some period of the year to initiate regular flowering. Overwatering of cacti is the single biggest cause of plant loss. Cacti are subject to Fusarium infections in their vascular cambium (the bundle of fibers and the "ring" inside the center of a cactus visible when cut in cross section) when overwatered or maintained in soils with high organic content. Fusarium mycelium typically grow into the cambium channels and plug up the plants transport system, causing tissue death and the classic rotting and collapsing observed when you overwater a cactus plant. Cacti are easy to grow if allowed to dry completely between waterings. Many species have specific periods of dormancy and should not be watered during these periods.

Uses

Cacti, cultivated by people worldwide, are a familiar sight as potted plants, houseplant
Houseplant
A houseplant is a plant that is grown indoors in places such as residences and offices. Houseplants are commonly grown for decorative purposes, positive psychological effects, or health reasons such as indoor air purification...

s or in ornamental gardens in warmer climates. They often form part of xeriphytic (dry) gardens
Xeriscaping
Xeriscaping and xerogardening refers to landscaping and gardening in ways that reduce or eliminate the need for supplemental water from irrigation...

 in arid regions, or raised rockeries. Some countries, such as Australia, have water restrictions in many cities, so drought-resistant plants are increasing in popularity. Numerous species have entered widespread cultivation, including members of Echinopsis
Echinopsis
Echinopsis is a large genus of cacti native to South America, sometimes known as hedgehog cacti, sea-urchin cactus or Easter lily cactus. One small species, E. chamaecereus, is known as the peanut cactus. The 128 species range from large and treelike types to small globose cacti...

, Mammillaria
Mammillaria
The genus Mammillaria is one of the largest in the cactus family , with currently 171 known species and varieties recognized. Most of the mammillarias are native to Mexico, but some come from the southwest USA, the Caribbean, Colombia, Venezuela, Guatemala and Honduras.The first was described by...

and Cereus
Cereus
Cereus is a genus of cactus. The term cereus is also used to describe cacti with very elongated bodies, including columnar growth cacti and epiphytic cacti...

among others.

Cacti can be used for fencing material where there is a lack of either natural resources or financial means to construct a permanent fence. This is often seen in arid
Arid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...

 and warm climates, such as the Maasai Mara in Kenya. This is known as a cactus fence
Cactus fence
A cactus fence is a hedge or fence made of closely spaced cactus plants, sometimes with barbed wire or wood interwoven with the cacti.Such fences are inexpensive to develop in regions where cacti are common, and can provide an extreme deterrent to any but a determined human intruder...

. Cactus fences are often used by homeowners and landscape architect
Landscape architect
A landscape architect is a person involved in the planning, design and sometimes direction of a landscape, garden, or distinct space. The professional practice is known as landscape architecture....

s for home security purposes. The sharp thorns of the cactus deter unauthorized persons from entering private properties, and may prevent break-ins if planted under windows and near drainpipes.

Many species of cacti have commercial uses; some cacti bear edible fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, such as the prickly pear
Opuntia
Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...

 and Hylocereus
Hylocereus
Hylocereus is a genus of cacti, often referred to as nightblooming cactus . Several species have large edible fruits, which are known as pitaya or dragonfruits.-Taxonomy:...

, which produces dragon fruit or pitaya
Pitaya
A pitaya or pitahaya is the fruit of several cactus species, most importantly of the genus Hylocereus . These fruits are commonly known as dragon fruit – cf...

. The edible cactus, or nopal
Nopal
Nopales are a vegetable made from the young cladode segments of prickly pear, carefully peeled to remove the spines. These fleshy pads are flat and about hand-sized. They can be purple or green...

, industry in Mexico is worth $150 million each year and approximately 10,000 farmers cultivate the plant. Opuntia
Opuntia
Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...

are also used as host plants for cochineal bugs in the cochineal
Cochineal
The cochineal is a scale insect in the suborder Sternorrhyncha, from which the crimson-colour dye carmine is derived. A primarily sessile parasite native to tropical and subtropical South America and Mexico, this insect lives on cacti from the genus Opuntia, feeding on plant moisture and...

 dye industry in Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

. Particularly in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 dead pillar cacti can yield valuable wood for construction. Some cacti are also of pharmaceutical significance.

The peyote
Peyote
Lophophora williamsii , better known by its common name Peyote , is a small, spineless cactus with psychoactive alkaloids, particularly mescaline.It is native to southwestern Texas and Mexico...

, Lophophora williamsii, is a well-known psychoactive agent used by Native Americans in the southwestern United States. Some species of Echinopsis
Echinopsis
Echinopsis is a large genus of cacti native to South America, sometimes known as hedgehog cacti, sea-urchin cactus or Easter lily cactus. One small species, E. chamaecereus, is known as the peanut cactus. The 128 species range from large and treelike types to small globose cacti...

also have psychoactive properties. For example, the San Pedro cactus, a common specimen found in many garden centers, is known to contain mescaline
Mescaline
Mescaline or 3,4,5-trimethoxyphenethylamine is a naturally occurring psychedelic alkaloid of the phenethylamine class used mainly as an entheogen....

.

Some species have become endangered in the wild because of overharvesting for sale as an ornamental plant. All cacti are covered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and many species, by virtue of their inclusion in Appendix 1, are fully protected.

Etymology

The word cactus is derived through Latin from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 κάκτος kaktos, which referred to the cardoon
Cardoon
The cardoon , also called the artichoke thistle, cardone, cardoni, carduni or cardi, is a thistle-like plant in the aster family Asteraceae. It is the naturally occurring form of the same species as the globe artichoke, and has many cultivated varieties...

 (Cynara cardunculus). Linnaeus
Carolus Linnaeus
Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...

in 1753 applied this name generically to a genus he called Cactus, which was later reassigned as a family, Cactaceae, and subdivided into multiple genera. Cactuses, the Latin plural cacti, the Greek plural cactoi and the uninflected plural cactus are all used in English.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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