This symposium deals with the origin and evolution of floristic elements and selected plant groups in deserts. Deserts cover about one fifth of the Earth's surface and occur where rainfall is less than 50 cm/year. Deserts comprise landscapes that are subjected to extremes of temperature, high evapo-transpiration, unpredictable precipitation, and complex soil types. The extreme nature of these desert environments presents numerous difficulties to the plants that inhabit them. Plants have developed a number of adaptations to cope with these harsh conditions. The symposium will address the systematics and biology of particular plant groups that are important constituents of deserts. Patterns of desert flora will be discussed as well as the hypotheses concerning the origin of particular floras.

Key words: adaptations, biogeography, desert, evolution, plant, systematics