- This article is about the desert plant. For the Texas town, see Cactus, Texas.
A cactus (plural, cacti or cactuses) is a type of (usually) succulent plant belonging to the dicotyledonous
flowering plant family, Cactaceae. The Cactaceae has
(depending upon the authority) between 24 and 220 genera, with around 90 genera being the most widely accepted count, and with
anywhere from 1,500 to 1,800 species. Cacti are well-known natives of the Americas,
mostly in desert areas. Some are also rainforest epiphytes, growing on tree branches where, despite the
high rainfall, water drains off quickly so that "dry" conditions prevail much of the time.
Cacti are almost exclusively New World plants. This means that they are native
only in North America and South America. There is however one exception, Rhipsalis baccifera; this species has a pantropical
distribution, occurring in the Old World in tropical Africa, Madagascar and Sri Lanka as well as in tropical America. This plant is thought to be a relatively recent colonist in the Old
World (within the last few thousand years), probably carried as seeds in the digestive tracts of migratory birds. Many other cacti have become naturalized to similar environments in other parts of the world after being
introduced by man.
Although many other succulent plants exist in the Old World, even
a few with spines, they are not cacti because they lack areoles. These specialized
structures are unique to cacti and identify the family.
Cacti are believed to have evolved in the last 30 to 40 million years. Long ago, the Americas were joined to the other
continents, but separated due to continental drift. Unique
species in the New World must have developed after enough the continents had moved
apart. Significant distance between the continents was only achieved around in the last 50 million years. It is assumed this
explains why cacti do not occur in Africa; the continents had already separated when cacti evolved.
Like other succulents, cacti are well-adapted to life with little precipitation. The leaves have evolved into spines, which in addition to allowing less water to evaporate than
regular leaves, defend the cactus against water-seeking animals. Photosynthesis is carried out by enlarged stems, which
also store water. Unlike many other succulents, the stem is the only part of a true cactus where this takes place. 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 and Pereskiopsis, do however retain large, non-succulent
leaves 5-25 cm long, and also non-succulent stems; they are possibly primitive genera, thought to be closely similar to the
plants that cacti evolved from.
Cacti come in many varieties in a wide range of shapes and sizes. Some grow to great size. Some cacti produce beautiful
flowers, which like spines and branches arise from areoles. Many cactus species are night-blooming, as they are pollinated by
nocturnal insects or small animals,
principally moths and bats. Cacti range from small and
round to pole-like and tall, such as the Saguaro.
A number of cactus species are cultivated for use as houseplants, as well as for ornamental gardens. They often form part of
xerophilic (dry) gardens in arid regions. Some cacti bear edible fruit.
Genera
- Acanthocalycium Backeb.
- Acanthocereus (Engelm. ex Berger) Britt. & Rose - Triangle cactus
- Acharagma N.P. Taylor
- Ancistrocactus
- Ariocarpus Scheidw. -
Livingrock
- Armatocereus
Backeb.
- Arrojadoa Britt. &
Rose
- Arthrocereus A.
Berger
- Astrophytum Lem.
- Austrocactus Britt.
& Rose
- Austrocylindropuntia Backeb.
- Aztekium Boed.
- Bergerocactus Britt.
& Rose - Snakecactus
- Blossfeldia Werderm.
- Brachycereus Britt.
& Rose
- Brasilicereus
Backeb.
- Brasilopuntia
(Schumann) Berger
- Browningia Britt. &
Rose
- Calymmanthium
F.Ritter
- Carnegiea Britton & Rose - Carnegia cactus, Saguaro
- Cephalocereus Pfeiff.
- Old man cactus
- Cephalocleistocactus F. Ritter
- Cereus P. Mill. - sweetpotato cactus
- Cintia Riha
- Cipocereus F.Ritter
- Cleistocactus Lem.
- Cochemeia (K. Brandegee)
Walton
- Coleocephalocereus Backeb.
- Consolea Lemaire
- Copiapoa Britt. & Rose
- Corryocactus Britt.
& Rose
- Coryphantha (Engelm.)
Lem. - Beehive cactus
- Cumulopuntia F.
Ritter
- Cylindropuntia
(Engelmann) F.M. Knuth
- Dendrocereus Britt.
& Rose
- Denmoza Britt. & Rose
- Discocactus Pfeiff.
- Disocactus Lindley.
- Echinocactus Link & Otto - Barrel cactus
- Echinocereus Engelm. -
Hedgehog cactus
- Echinomastus Britt.
& Rose
- Echinopsis Zucc.
- Epiphyllum Haw. - Climbing cactus
- Epithelantha A. Weber
ex Britt. & Rose - Pingpong ball cactus
- Eriosyce Phil.
- Escobaria Britt. & Rose - Foxtail cactus, Pincushion cactus
- Escontria Rose
- Espostoa Britt. & Rose
- Espostoopsis
Buxbaum
- Eulychnia Phil.
- Facheiroa Britt. &
Rose
- Ferocactus Britt. & Rose - Barrel cactus
- Frailea Britt. & Rose
- Geohintonia Glass &
Fitz Maurice
- Grusonia F. Reichenbach
- Gymnocalycium Pfeiff. - Chin cactus
- Haageocereus
Backeb.
- Harrisia Britt. - Applecactus
- Hatiora Britt. & Rose
- Hylocereus (Berger) Britt.
& Rose - Nightblooming cactus
- Isolatocereus
Backeb.
- Jasminocereus Britt.
& Rose
- Lasiocereus F.
Ritter
- Lemaireocereus
- Leocereus Britt. &
Rose
- Lepismium
- Leptocereus (Berger)
Britt. & Rose
- Leuchtenbergia
Hooker
- Lobivia Britt. & Rose
- Lophophora Coult. - Peyote
- Maihuenia (Philippi ex
F.A.C.Weber) K.Schumann
- Maihueniopsis
- Mammillaria Haw. - Fishhook cactus, Globe cactus, Pincushion cactus, Bird's-nest cactus
- Mammilloydia
Buxbaum
- Matucana Britt. & Rose
- Melocactus Link &
Otto
- Micranthocereus
Backeb.
- Mila Britt. & Rose
- Melocactus Link &
Otto
- Myrtillocactus
Console
- Neobuxbaumia
Backeb.
- Neolloydia Britt. &
Rose
- Neoraimondia Britt.
& Rose
- Neowerdermannia
Fric
- Notocactus (K.Schum.)
Fric
- Obregonia Fric
- Opuntia P. Mill. - Prickly pear, Cholla
- Oreocereus Riccob.
- Oroya Britt. & Rose
- Ortegocactus Alex.
- Pacherocactus G.D.
Rowley
- Pachycereus (Berger)
Britt. & Rose
- Parodia Speg.
- Pediocactus Britt. &
Rose - Hedgehog cactus
- Pelecyphora
Ehrenberg
- Peniocereus (Berger)
Britt. & Rose
- Pereskia P. Miller
- Pereskiopsis Britt.
& Rose
- Pilosocereus Byles
& Rowley - Tree cactus
- Polaskia Backeberg
- Praecereus Buxbaum
- Pseudoacanthocereus F. Ritter
- Pseudorhipsalis
Britt. & Rose
- Pterocactus K.
Schumann
- Pygmaeocereus H.
Johnson & Backeb.
- Quiabentia Britt. &
Rose
- Rauhocereus
Backeberg
- Rebutia K. Schumann
- Rhipsalis Gaertn.
- Samaipaticereus
Cardenas
- Schlumbergera Lem. - Holiday Cactus
- Sclerocactus Britt.
& Rose - Fishhook
cactus
- Selenicereus (Berger)
Britt. & Rose - Moonlight
cactus, Night blooming cereus
- Setiechinopsis
Backeb. ex de Haas
- Stenocereus (Berger) Riccob. Organ pipe cactus and
others
- Stephanocereus A.
Berger
- Stetsonia Britt. &
Rose
- Strombocactus Britt.
& Rose
- Sulcorebutia
Backeberg
- Tacinga Britt. & Rose
- Tephrocactus
Lemaire
- Thelocactus (K. Schum.)
Britt. & Rose
- Trichocereus - San Pedro
- Tunilla D.R. Hunt &
Iliff
- Turbinicarpus Buxbaum
& Backeberg - Top cactus
- Uebelmannia Buining
- Weberbauercereus Backeberg
- Weberocereus Britt.
& Rose
- Weingartia Werderm.
- Yavia R. Kiesling & J. Piltz
- Yungasocereus F.
Ritter
Reference
- Edward F.
Anderson, The Cactus Family (Timber Press, 2001) ISBN 0-88192-498-9 - Comprehensive and lavishly illustrated
External links
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