A cactus is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word "cactus" derives, through Latin, from the Ancient Greek κάκτος, kaktos, 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. Most cacti live in habitats subject to at least some drought. 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. 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 leaves, enlarged stems carry out photosynthesis. Cacti are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north—except for Rhipsalis baccifera, which also grows in Africa and Sri Lanka.
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.
Pereskia is a small genus of about four species of cacti that do not look much like other types of cacti, having substantial leaves and non-succulent stems. The genus is named after Nicolas-Claude Fabri de Peiresc, a 16th-century French botanist. The genus was more widely circumscribed until molecular phylogenetic studies showed that it was paraphyletic. The majority of species have since been transferred to Leuenbergeria and Rhodocactus. Although Pereskia does not resemble other cacti in its overall morphology, close examination shows spines developing from areoles, and the distinctive floral cup of the cactus family. Pereskia is believed to resemble the ancestor of all cacti.
Didiereaceae is a family of flowering plants found in continental Africa and Madagascar. It contains 20 species classified in three subfamilies and six genera. Species of the family are succulent plants, growing in sub-arid to arid habitats. Several are known as ornamental plants in specialist succulent collections. The subfamily Didiereoideae is endemic to the southwest of Madagascar, where the species are characteristic elements of the spiny thickets.
Ariocarpus is a small genus of succulent, subtropical plants of the family Cactaceae.
Pereskiopsis is a genus of cactus in the subfamily Opuntioideae. Unlike typical cacti, it has persistent fleshy leaves. The genus name refers to its resemblance to the genus Pereskia. Most species are found in Mexico south through Guatemala to Honduras, with one species in Bolivia. The incorrect spelling Peireskiopsis has also been used.
Corynopuntia, also known as club chollas, is a genus in the family Cactaceae, established by Knuth in 1935. Molecular phylogenetic studies suggest that it should be included in Grusonia, a view accepted by Plants of the World Online as of June 2021.
Rhodocactus is a genus of flowering plant in the cactus family Cactaceae, native to central South America. Unlike most species of cacti, Rhodocactus has persistent leaves and a fully tree-like habit. The genus was sunk into a broadly circumscribed Pereskia, but molecular phylogenetic studies from 2005 onwards showed that with this circumscription Pereskia was paraphyletic, and in 2016, Rhodocactus was restored for southern South American species.
Glochids or glochidia are hair-like spines or short prickles, generally barbed, found on the areoles of cacti in the sub-family Opuntioideae. Cactus glochids easily detach from the plant and lodge in the skin, causing irritation upon contact. The tufts of glochids in the areoles nearly cover the stem surfaces of some cactus species, each tuft containing hundreds of glochids; this may be in addition to, or instead of, the larger, more conspicuous cactus spines, which do not readily detach and are not generally barbed.
Opuntioideae is a subfamily of the cactus family, Cactaceae. It contains 15 genera divided into five tribes. The subfamily encompasses roughly 220-250 species, and is geographically distributed throughout the New World from Canada, to Argentina. Members of this subfamily have diverse habits, including small geophytes, hemispherical cushions, shrubs, trees, and columnar cacti consisting of indeterminate branches or determinate terete or spherical segments.
Rhipsalis pilocarpa, the hairy-fruited wickerware cactus, is a species of flowering plant in the cactus family that is endemic to Brazil. Scarce in the wild, it is known only in a small number of isolated locations. Its status is listed as “vulnerable” by the IUCN Red List. However, it is cultivated as an ornamental houseplant and as such has gained the Royal Horticultural Society’s Award of Garden Merit.
Parodia buiningii is a rare species of cactus native to South America. It is a solitary spherical or oblate cactus only a few inches in height with long, yellow spines. It bears yellow flowers, and produces hairy fruit and black seeds. It is found surrounding the towns of Santana do Livramento, Brazil and Rivera, Uruguay.
Mammillaria spinosissima, also known as the spiny pincushion cactus, is a species of flowering plant in the cactus family Cactaceae, endemic to the central Mexican states of Guerrero and Morelos, where they grow at elevations of approximately 1,600 to 1,900 metres. The species was described in 1838 by James Forbes, gardener of the Duke of Bedford. Botanist David Hunt collected a specimen in 1971, when he located one near Sierra de Tepoztlan, Mexico.
In plant morphology, thorns, spines, and prickles, and in general spinose structures, are hard, rigid extensions or modifications of leaves, roots, stems or buds with sharp, stiff ends, and generally serve the same function: physically deterring animals from eating the plant material.
Parodia arnostiana is a species of cactus in the genus Parodia. The small, squat green plants produce yellow flowers, green fruit and black seeds. The species is found growing in Rio Grande do Sul, Brazil.
Escobaria sneedii is a rare species of cactus known by the common names Sneed's pincushion cactus and carpet foxtail cactus. It is native to the Chihuahuan Desert, where it occurs in scattered locations in New Mexico, Texas, and Chihuahua. Some plants occurring in Arizona may be included within this species. Botanical authors do not necessarily agree on the circumscription of this species. Most will agree at this point in the research, however, that there are two varieties of Escobaria sneedii, and that both are rare and endangered. The plant is popular with cactus enthusiasts and dealers because of its often petite size and tolerance for moderately cold climates. They have been overharvested from their natural habitat, the main reason why the two varieties, var. sneedii and var. leei, have been federally listed as endangered and threatened, respectively.
Schlumbergera gaertneri, formerly Hatiora gaertneri, is a species of epiphytic cactus which belongs to the tribe Rhipsalideae within the subfamily Cactoideae of the Cactaceae. Together with the hybrid with S. rosea, Schlumbergera × graeseri, it is known as Easter cactus or Whitsun cactus and is a widely cultivated ornamental plant. It has received the Royal Horticultural Society's Award of Garden Merit.
Echinocereus dasyacanthus is a member of the cactus family, Cactaceae. It is one of about 2000 total species belonging to this family. The cactus is commonly known as Texas rainbow cactus because of the subtle rings or bands of contrasting colors along the stem of the plant. Not all Texas rainbow cacti have the "rainbow" coloration on their stems. Another common name is spiny hedgehog cactus.
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.
Mammillaria fraileana is one of about 200 species of the genus Mammillaria from the cactus family Cactaceae. This species is native to Mexico and can be found along the east coast of the southern part of Baja California Peninsula in Desert Scrub communities. They tend to grow in non calcareous dry granite-based soil but can also grow in rocky habitats, either in rock fissures or directly on top of the rock surface even without the presence of soil. Thus, the mineral composition of the rocks in their habitat directly influence their abundance. The habitat of Mammillaria fraileana is home to succulent flora and is particularly rich in local endemics. Currently, no major threats to the species are known to exist.
