Phycology is the study of algae, the primary photosynthetic organisms in freshwater and marine food chains. As a food source for zooplankton and filter-feeding shellfish, the algae are an extremely important group. Since the publication of the first edition in 1981, this textbook has established itself as a classic resource on phycology. This revised edition, first published in 2008, maintains the format of previous editions, whilst incorporating more recent information from nucleic acid sequencing studies. Detailed life-history drawings of algae are presented alongside information on the cytology, ecology, biochemistry, and economic importance of selected genera. Phycology is suitable for upper-level undergraduate and graduate students following courses in phycology, limnology or biological oceanography. Emphasis is placed on those algae that are commonly covered in phycology courses, and encountered by students in marine and freshwater habitats.