This book was originally published in 1983, and it provides information regarding ecological conditions and population dynamics of both marine and freshwater algae form diverse habitats. Unfavourable environmental conditions induce the production of resting spores in certain organisms. Many algae have successfully developed specialized resistant characteristics that give them considerable evolutionary advantages over organisms that are unable to withstand periods of extreme change in their environment. Though the resting spore is considered to be an advantageous and primitive trait, the benefits are offset by the great amount of energy needed to produce and maintain the cell in near-dormancy over long periods of time and by the potentially 'lost' number of cell divisions that could have occurred during the resting phase. The interesting contrast of advantages and disadvantages has stimulated biologists to investigate the morphology and the underlying processes of the physiology of vegetative cells and thick-walled resting spores.