Barrel Cactus: Genus Ferocactus
- Information on this family of cacti, with photographs and descriptions of several species found in Arizona.
- http://www.desertusa.com/mag99/june/papr/barrelcactus.html

Ferocactus
- Images and culture of many species of barrel cactus.
- http://www.desert-tropicals.com/Plants/Cactaceae/Ferocactus.html

Ferocactus stainesii
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- http://florawww.eeb.uconn.edu/acc_num/198502309.html

Ferocactus latispinus
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- http://florawww.eeb.uconn.edu/acc_num/198800213.html

Ferocactus pottsii
- image
- http://www.dipbot.unict.it/orto/1039-1.html