This monograph provides knowledge on the systematics, synonymy, morphology and ecology of benthonic algae and periphyton of Lake Baikal. It has been found that the lake is inhabited by 137 meio- and macrophyte species among which most common are green and blue-green algae. This work includes illustrated diagnoses of all taxa and keys to their identification. Special attention is focused on endemic genera and species. Peculiarities of vertical and horizontal distribution of these algae, and seasonal variations in their composition and quantitative distribution are considered. This book is intended for botanists, algologists, hydrobiologists, teachers and students of biological faculties.