A cactus is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1,750 known species of the order Caryophyllales. The word cactus derives, through Latin, from the Ancient Greek word κάκτος (káktos), a name originally used by Theophrastus for a spiny plant whose identity is now not certain. Cacti occur in a wide range of shapes and sizes. They are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north, with the exception of Rhipsalis baccifera, which is also found in Africa and Sri Lanka. Cacti are adapted to live in very dry environments, including the Atacama Desert, one of the driest places on Earth. Because of this, cacti show many adaptations to conserve water. For example, almost all cacti are succulents, meaning they have thickened, fleshy parts adapted to store water. Unlike many other succulents, the stem is the only part of most cacti where this vital process takes place. 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. In the absence of true leaves, cacti's enlarged stems carry out photosynthesis.
Mammillaria is one of the largest genera in the cactus family (Cactaceae), with currently 200 known species and varieties recognized. Most of the mammillaria are native to Mexico, but some come from the southwest United States, the Caribbean, Colombia, Venezuela, Guatemala and Honduras. The common name "pincushion cactus" refers to this and the closely related genus Escobaria.
Cylindropuntia bigelovii, the teddy-bear cholla, is a cholla cactus species native to Northwestern Mexico, and to the United States in California, Arizona, and Nevada.
Cleistocactus strausii, the silver torch or wooly torch, is a perennial flowering plant in the family Cactaceae. It is native to mountainous regions of Department Tarija, Bolivia, at 1,500–3,000 m (4,921–9,843 ft).
Bergerocactus emoryi is a species of cactus, known commonly as the golden-spined cereus, golden snake cactus, velvet cactus or golden club cactus. It is a relatively small cactus, but it can form dense thickets or colonies, with the dense yellow spines giving off a velvety appearance when backlit by the sun. From April to May, yellow, green-tinged flowers emerge, which transform into reddish, globular fruit. This species is native to the California Floristic Province, and is found in northwestern Baja California and a small part of California, in San Diego County and on the southern Channel Islands. Where the Mediterranean climate of the California Floristic Province collides with the subtropical Sonoran Desert near El Rosario, hybrids with two other species of cacti are found. It is the sole member of the monotypic genus Bergerocactus, named after German botanist Alwin Berger.
Leocereus is a genus of cactus. Its only species is Leocereus bahiensis, first described by Nathaniel Lord Britton and Joseph Nelson Rose in 1926.
Oreocereus is a genus of cacti, known only from high altitudes of the Andes. Its name means "mountain cereus", formed from the Greek prefix oreo- and the Neo-Latin cereus, meaning wax or torch.
Mila caespitosa is a species of cacti and the only species of the genus Mila. Its generic name is an anagram of Lima, Peru, the city near which the plant is found. The genus was first thought to comprise 13 species, until recent studies suggest they form one very variable species.
Kroenleinia grusonii, popularly known as the golden barrel cactus, golden ball or mother-in-law's cushion, is a species of barrel cactus which is endemic to east-central Mexico.
Selenicereus grandiflorus is a cactus species originating from the Antilles, Mexico and Central America. The species is commonly referred to as queen of the night, night-blooming cereus, large-flowered cactus, sweet-scented cactus or vanilla cactus. The true species is extremely rare in cultivation. Most of the plants under this name belong to other species or hybrids. It is often confused with the genus Epiphyllum.
Pereskia aculeata is a scrambling shrub in the family Cactaceae. Common names include Barbados gooseberry, blade-apple cactus, leaf cactus, rose cactus, and lemonvine. It is native to tropical America. The leaves and fruits are edible, containing high quantities of protein, iron and other nutrients, and it is a popular vegetable in parts of the Brazilian state of Minas Gerais under the name of ora-pro-nóbis.
Cereus ( "serious") is a genus of cacti including around 33 species of large columnar cacti from South America. The name is derived from Greek (κηρός) and Latin words meaning "wax", "torch" or "candle". Cereus was one of the first cactus genera to be described; the circumscription varies depending on the authority. The term "cereus" is also sometimes used for a ceroid cactus, any cactus with a very elongated body, including columnar growth cacti and epiphytic cacti.
Opuntia macrocentra, the long-spined purplish prickly pear or purple pricklypear, is a cactus found in the lower Southwestern United States and Northwestern Mexico. A member of the prickly pear genus, this species of Opuntia is most notable as one of a few cacti that produce a purple pigmentation in the stem. Other common names for this plant include black-spined pricklypear, long-spine prickly pear, purple pricklypear, and redeye prickly pear.
Pachycereus pecten-aboriginum is a columnar cactus plant native to Mexico. They can grow up to 15 m (49 ft) high. The trunk of this species is 1.2 to 5.0 m tall and the fruits are large and burr-like. The specific name, pecten-aboriginum, is from the Latin, and means "native combs". It was inspired by the use of the fruits as hair combs.
Arachnoid organs, such as leaves or stems, have an external appearance similar to cobwebs – the appearance of being covered with fine, white, usually tangled hairs. This can cause plants to appear grey or white. The arachnoid appearance is common on the leaves and stems of various sclerophyllous members of the family Asteraceae, such as some thistles. The arachnoid appearance of Haworthia arachnoidea arises from the spinescent leaf denticles, and the arachnoid appearance of the cactus Cephalocereus senilis is from long-lasting hairy spines.
Mammillaria hahniana, the old lady cactus, is a species of flowering plant in the family Cactaceae, native to central Mexico. It grows to 25 cm (10 in) tall by 50 cm (20 in) broad. The solitary spherical stems, 12 cm in diameter, are covered in white down and white spines. Reddish purple flowers are borne in spring and summer, sometimes forming a complete ring around the apex of the plant.
Espostoa lanata is a species of cactus of the genus Espostoa.
Oreocereus trollii, commonly known as the Old Man of the Andes cactus, is a species of cacti native to Argentina and Bolivia. Though listed as Least Concern by the IUCN, the plant is collected extensively, and in some areas is threatened.
Cephalocereus macrocephalus, synonym Neobuxbaumia macrocephala, is a species of cactus endemic to Mexico.
Cephalocereus polylophus is a species of cactus endemic to Mexico. Often grown under the synonym Neobuxbaumia polylopha, it is popular with cactus growers and reproduces well in cultivation.
