The Didiereaceae comprise one of seven endemic Families of flowering plants in the Malagasy Republic. . Werner Rauh, who has explored, introduced and described the Madagascan succulents with astonishing thoroughness and fervour, has written many impassioned pleas for the conservation of what remains of these plants on Madagascar. Habitat destruction is still going on in the name of agriculture to make way for the advance of another succulent: Agave sisalana, vast armies of which are taking over the landscape as a source of the industrial fibre sisal. This booklet - largely a digest and translation of Rauh's classic researches, covers the single Family of four genera and ten or eleven species.