Sometimes called "Living Stones".
Mammillaria is one of the larger genera in the Cactus family, and one of the most variable.
There are about 100 succulent Senecios.
Thankfully the hall has a high ceiling.
Many from Madagascar, some from Africa and Asia in or near India.
Stapeliads are mainly from Southern Africa. They are called carrion flowers because of the smell they emit to attract flies for pollination.
Ferocactus are fierce cacti from Mexico and Southern USA. Leuchtenbergia consists of a single species, from Mexico.