This subject will focus on algae and plants of both marine submerged and emerged environments and particularly on marine microalgae, macroalgae and seagrasses and on terrestrial plants belonging to costal vegetation, with a special emphasis on those typical of Mediterranean and tropical regions. In the introductory part of the course attention will be paid in analysing the main evolutionary stages which have led to the actual biodiversity of marine algae and plants and in deeping in the knowledge on the major taxonomic groups of algae and plants that can be found in Mediterranean and tropical marine and costal environments. The following lessons will focus on the systematics of marine algae and seagrasses; a taxonomic classification will be conducted in an evolutionary key, based on the different kinds of photosynthetic pigments. Furthermore, the main morphological, biological and ecological features will also be described for the most important groups, as well as their environmental importance. The second part of the course, instead, will focus on costal vegetation of Mediterranean and tropical regions. Initially, a general characterization will be conducted, considering the main taxonomic groups of coastal plants, prior to describe in detail the vegetation of the most particular habitats (cliffs, estuaries, mangrove forests, etc.). The third part of the course will be dedicated to analyse the main environmental and human problems related to marine algae, such as biological invasions and harmful algal blooms. Finally, the last lessons will be organized as workshops, during which small groups of students will be asked to deep in their knowledge on the main uses of marine algae and plants and to share them with their mates.