This image is in the plant database under San Diego Barrel Cactus (Ferocactus viridescens)
This image is in the plant database under Euphorbia (Euphorbia esculenta)
This image is in the plant database under Old Man of the Andes (Oreocereus celsianus)
This image is in the plant database under Echeveria (Echeveria runyonii)
This image is in the plant database under Devil's Tongue Barrel (Ferocactus latispinus)
This image is in the plant database under Black-Spined Aloe (Aloe melanacantha)