Established in 1950, the International Organization for Succulent Plant Study (IOS) is a non-governmental organization promoting the study and conservation of succulent and allied plants and encouraging collaboration among scientists and curators of significant living collections of such plants, professional or amateur. We are affiliated to the International Union of Biological Sciences (IUBS) and have links with numerous botanical gardens, research institutions and conservation organizations, the latter including Botanic Gardens Conservation International (BGCI) and the International Union for the Conservation of Nature and Natural Resources (IUCN).

Succulents are a diverse group of plants, variously adapted by means of storage tissue in their leaves, stems and/or roots to withstand seasonal drought and other adverse conditions. Succulence has evolved in numerous plant families, some that are closely related but many that are not. Though many have very attractive flowers, the common asset that is the source of their appeal as ornamentals is the enormous diversity of habit and stem-form displayed by such groups as the cacti and succulent euphorbias, for instance, and by leaf-form and colour in others like the haworthias, aloes and echeverias. Numerous 'cactus and succulent societies' as well as commercial nurseries now exist to cater for amateur growers and collectors.

With its emphasis on research and conservation, both in the natural habitats where the plants grow and in well-maintained and documented living collections and herbaria elsewhere, IOS seeks to provide an international forum for discussion of scientific and other issues related to succulents. Over the years the IOS membership list has included the names of virtually all those individuals who have contributed significantly to knowledge of the plants. Since its founding meeting at Zürich in 1950, IOS has organized biennial congresses and other meetings throughout Europe and alternately in other countries with greater diversity of native succulents, notably North and South America, and southern Africa.

The proceedings of these meetings are summarized in the IOS Bulletin (now issued electronically) and the research etc that has been presented and discussed, and published in a wide range of scientific journals, books and other publications, is listed annually, along with details of all new names of succulent plants, in IOS Repertorium Plantarum Succulentarum. Numerous significant publications on the biology and diversity of succulent plants have been produced by IOS members, often in collaboration, including a recent series of benchmark volumes covering all groups of succulent plants (see Publications).

Since 1984, regular round-table meetings have been held under the auspices of the IOS to discuss the classification of the Cactaceae. In the face of the radically contrasting views then held on the classification of the family, this informal 'IOS Working Party', later renamed the International Cactaceae Systematics Group, developed a classified list of genera to reflect a consensus of the opinions of the contributors and to serve as a basis for further discussion and research. This approach led the Plants Committee of CITES (the Convention on International Trade in Endangered Species) to commission IOS to compile a checklist of the family for the use of its Scientific Authorities worldwide. The resulting CITES Cactaceae Checklist, as well as fulfilling its intended purpose, proved a best-seller among cactus enthusiasts and is maintained and periodically updated to provide a more widely acceptable and stable framework for continuing research and discussion than has been available hitherto. The initial 'consensus' classification, adopted or amended in numerous publications since its first publication in 1986, and the willingness of members of the working group, both professional and amateur, to collaborate and pool their resources, has stimulated basic research on various topics, including a range of molecular systematic studies that are leading to a much deeper understanding of the phylogeny of the family, its component genera, and their classification.

IOS is a strong advocate of conservation and became the first plant organization to publish a Code of Conduct, including guidelines for field research, collection maintenance, and treatment of field-collected material, to which all members are requested to adhere.

IOS contributes substantially to the International Union for Conservation of Nature and Natural Resources (IUCN). The IUCN Species Survival Commission's (IUCN/SSC) Cactus and Succulent Specialist Group (CSSG) was set up on the recommendation of IOS and includes many IOS members. It has undertaken important conservation fieldwork in several countries and produced a fundamental Action Plan to ensure long-term survival of endangered taxa of cacti and other succulents. Currently, the CSSG participates actively in the IUCN Global Cactus Assessment, a project aimed at assessing all cactus species under the current Red List criteria. In association with Botanic Gardens Conservation International (BGCI), IOS is now reviving an earlier IOS initiative to promote the establishment of a network of 'Reserve Collections' of living cacti and other succulent plants and proposing measures to assess and enhance the potential of these collections as a resource for research and conservation.

The IOS Board invites active succulent plant researchers, students, and other qualified individuals and organizations seriously interested in supporting the study of such plants to join us and help us achieve our objectives. (see Membership).

David Hunt