As a result of living in extremely dry areas, these species have specialized tissues which accumulate water in their leaves, stems or roots, creating a hydric reserve for use during the long periods of drought common in their natural habitat. Also known as fat plants, they are found in tropical and subtropical areas of America and Africa.

This is an extremely varied collection in terms of both the genera and families to which it is home and the size and shape of the species themselves and the way in which they adapt to their environment. The families on show are the Agavaceae, Aizoaceae, Aloaceae, Apocynaceae, Asclepidaceae, Cactaceae, Crassulaceae, Dracaenaceae, Euphorbiaceae, Hyacinthaceae, Portulacaceae and Vitaceae.