Mammillaria is one of the larger genera in the Cactus family, and one of the most variable, but only some have hooked spines.

Crest and monstose are mutations of the cellular structure.

A genus of cacti from the dry coastal deserts, particularly the Atacama Desert, of northern Chile.

Ariocarpus is one of the treasures of the world of Cacti, from Central to Northern Mexico and Southern Texas. Obregonia, the artichoke cactus, is a genus of cacti with a single species, from Mexico.

Astrophytum (Bishop's Hat) is a (mostly) star shaped cactus from north/central Mexico and southern Texas, USA.

Melocactus are recognizable by the large cephalium that develops on mature plants. They are native from Brazil to Southern Mexico, including the Caribbean.

Four genera from the subfamily Opuntioideae, all from the Americas.

Parodia, native to the uplands of Argentina, Peru, Bolivia, Brazil, Colombia and Uruguay. Notocactus, with the center of the genus in Brazil and Argentina, but with members throughout the Eastern side of the Andes.

From Mexico and Southern US. Usually having heavy spination and relatively small flowers, the fruits are copiously woolly. Includes the "Golden Barrel Cactus".

Epiphytic cacti do not live in soil like other cacti but in places like rain forests they inhabit the forks or large branches of trees, their roots clinging tightly to their host. Epiphytes have specially designed stomata (leaf openings), that help absorb moisture from the open air.