Algae are ubiquitous. A multitude of species, ranging from microscopic unicells to gigantic kelps, inhabit the world's oceans, freshwater bodies, soils, rocks and trees. To understand the basic role of algae in the global ecosystem, a reliable and modern introduction to their kaleidoscopic diversity, systematics and phylogeny is indispensible. This volume provides such an introduction. The text represents a completely revised and updated edition of a highly acclaimed German textbook which was heralded for its clarity as well as its breadth and depth of information. This new edition takes into account recent re-evaluations in algal systematics and phylogeny which have been made necessary by insights provided by the powerful techniques of molecular genetics and electron microscopy, as well as more traditional life history studies.