Help building the largest human-edited directory of the web Suggest URL - Open Directory Project - Become an editor

directopedia.org uses links and structure from dmoz Open Directory Project.
The contents has been generating using technology developed by scientec.

This article is about the plant family. For the genus Cactus, see Mammillaria, Melocactus and Opuntia. For the Texas town, see Cactus, Texas.

? Cacti
Mexican Lime Cactus (Ferocactus pilosus) growing south of Saltillo, Coahuila, northeast Mexico
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Caryophyllales Family: Cactaceae Juss.
Genera
See Taxonomy of the Cactaceae

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 people.

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 the continents had moved apart. Significant distance between the continents was only achieved around in the last 50 million years. This may explain why cacti are so rare 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 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.

Selected important genera include the following; for a full list see Taxonomy of the Cactaceae

• Acanthocereus - triangle cactus
• Ariocarpus - living rock
• Bergerocactus - snakecactus
• Carnegiea - saguaro
• Cephalocereus - old man cactus
• Cereus - sweetpotato cactus
• Coryphantha - beehive cactus
• Echinocactus - barrel cactus
• Echinocereus - hedgehog cactus
• Echinopsis - San Pedro
• Epiphyllum - climbing cactus
• Epithelantha - pingpong ball cactus
• Escobaria - foxtail cactus, pincushion cactus
• Ferocactus - barrel cactus
• Gymnocalycium - Chin cactus
• Harrisia - applecactus
• Hylocereus - nightblooming cactus
• Lophophora - peyote
• Mammillaria - fishhook cactus, globe cactus, bird's-nest cactus
• Opuntia - prickly pear, cholla
• Pediocactus - hedgehog cactus
• Pilosocereus - tree cactus
• Schlumbergera - holiday cactus
• Sclerocactus - fishhook cactus
• Selenicereus - moonlight cactus, nightblooming cereus
• Turbinicarpus - top cactus

See also

• Plant
• Succulent

References and external links

• Anderson, Edward F. The Cactus Family (Timber Press, 2001) ISBN 0-88192-498-9 - Comprehensive and lavishly illustrated
• Benson, Lyman The Cacti of Arizona (The University of Arizona Press, 1981) ISBN 0-8165-0509-8 - Thorough treatment of the Arizona, U.S.A., species
• CactiGuide.com - many photos, and discussion forum
• Cactus portal
• Hydrocactus flowering Cacti videos
• Cactus Romania - growing cacti in East Europe

This article is based on the article "Cacti" from Wikipedia - the free encyclopedia created and edited by online user community. This article is distributed under the terms of GNU Free Documentation License. Here you find the list of authors of this article. The article can only edited within Wikipedia. Edit this article in Wikipedia.

Succulent plants, or succulents, are plants that store water in their enlarged fleshy leaves, stems, or roots. The enlargement is usually due to the greater amount of the parenchyma tissue, eg aloe vera plant.

Although all plants store water, succulent plants are especially adapted to store water for long periods. This allows them to survive in arid environments, where they receive little competition from other plants and less herbivory. During the day, their habitat is rather hot. However, the habitat is cooler at night allowing the succulents to respire. Often, morning dewfall helps the plants to survive: Using long hairs, that cover a large part of their surface, some succulents are able to absorb dew.

Many succulents have a waxy coating on their stems and leaves, helping them to retain moisture. Having a large internal volume for storage but minimum surface area is also important to prevent water loss. CAM photosynthesis is also a common water conservation feature found in many succulents.

Succulence is a feature due to convergent evolution and is not necessarily an indication of genetic relationship. There are succulents in many unrelated families (more or less 50, some sources note only 28). However, for some families, most members are succulent; for example the Cactaceae, Agavaceae, Aizoaceae, and Crassulaceae.

The table below shows the number of succulent species found in some families:

Family	Succulent #	Modified parts	Distribution
Agavaceae	300	Leaf	North and Central America
Cactaceae	1600	Stem	The Americas
Crassulaceae	1300	Leaf	Worldwide
Aizoaceae	2000	Leaf	Southern Africa
Apocynaceae	500	Stem	Africa, Arabia, India
Didiereaceae	11	Stem	Madagascar (endemic)
Euphorbiaceae	500	Stem and/or leaf	Africa, Madagascar, India
Asphodelaceae	500	Leaf	Africa, Madagascar
Portulacaceae	?	Leaf and stem	The Americas

External links

• http://www.sukkulenten.ch (in German)
• http://www.lapshin.org/succulent/ (English/Russian)
• http://www.bihrmann.com/caudiciforms/ (Caudiciform plants)

This article is based on the article "Succulents" from Wikipedia - the free encyclopedia created and edited by online user community. This article is distributed under the terms of GNU Free Documentation License. Here you find the list of authors of this article. The article can only edited within Wikipedia. Edit this article in Wikipedia.