Opuntia cholla
- Information and photographs of the Chain Link Cholla growing in the desert regions of Baja California.
- http://www.biology.ed.ac.uk/research/groups/jdeacon/desertecology/choimag2.htm#top

Opuntia basilaris
- Description of the Beavertail Cactus and information on its habitat and range, with several photographs.
- http://www.desertusa.com/april96/du_beavtail.html

Opuntia fulgida
- All about the Chain Fruit Cholla, description, photograph, range, habitat and scientific and common names.
- http://www.desertusa.com/mag98/may/papr/du_chaincholla.html

Cholla Cactus: Genus Opuntia
- Cholla is a name for various shrubby cacti of this genus with cylindrical stems composed of segmented joints. Photographs and information on several species.
- http://www.desertusa.com/mag99/may/papr/chollas.html

Opuntia leptocaulis
- Photograph and description of the Desert Christmas Cactus and information on its habitat and range.
- http://www.desertusa.com/mag98/dec/papr/xmascactus.html

Prickly Pear Cactus
- Information on these cacti with photographs and descriptions of several species found in Arizona.
- http://www.desertusa.com/magoct97/oct_pa/du_prkpear.html

Prickly Pears and Chollas
- Descriptions, ecology and images.
- http://www.biology.ed.ac.uk/research/groups/jdeacon/desertecology/opuntia.htm

Looking at a Cactus with the QX5 Microscope
- Rudolf Baumueller turns his microscope on the cactus, Opuntia, and produces a photographic study of the plant.
- http://www.microscopy-uk.org.uk/mag/artaug06/rb-qx5.html

Opuntia humifusa
- Species summary from the USDA Forest Service.
- http://www.fs.fed.us/database/feis/plants/cactus/opuhum/all.html

Opuntia polycantha
- Species summary from the USDA Forest Service.
- http://www.fs.fed.us/database/feis/plants/cactus/opupol/all.html

Opuntia arenaria - Dune Pricklypear
- Image, description, and range of this rare plant in New Mexico.
- http://nmrareplants.unm.edu/rarelist_single.php?SpeciesID=122

Opuntia viridiflora - Santa Fe Cholla
- Description, image, and range of this rare plant in New Mexico.
- http://nmrareplants.unm.edu/rarelist_single.php?SpeciesID=61

Genus Opuntia
- Description of the genus and its species in the Sonoran Desert, Arizona. Includes illustrations.
- http://www.desertmuseum.org/books/opuntia.html

Opuntia
- Description and culture.
- http://www.botany.com/opuntia.html

Opuntia leptocaulis - Desert Christmas Cactus
- Images from Arizona.
- http://www.naturesongs.com/vvplants/christmascactus.html

Opuntia phaeacantha - Desert Prickly Pear
- Images from Arizona.
- http://www.naturesongs.com/vvplants/desertpricklypear.html

Opuntia tomentosa
- image
- http://www.dipbot.unict.it/orto/0120-1.html

Opuntia stricta
- image
- http://www.dipbot.unict.it/orto/0119-1.html

Opuntia schumannii
- image
- http://www.dipbot.unict.it/orto/0118-1.html

Opuntia linguiformis
- image
- http://www.dipbot.unict.it/orto/1053-1.html

Opuntia ficus-indica
- image
- http://www.dipbot.unict.it/orto/0116-1.html

Opuntia fragilis
-
- http://florawww.eeb.uconn.edu/acc_num/198502292.html

Opuntia microdasys
-
- http://florawww.eeb.uconn.edu/acc_num/198502330.html