Algae

Summary

Algae are any of a large and diverse group of photosynthetic organisms. It excludes the land plants (embryophytes). Such organisms range from microscopic unicellular microalgae to seaweeds, multicellular macroalgae which may grow up to 50 metres (160 ft) in length. Most algae are aquatic, and some form cohesive colonies. Freshwater algae include Charophyta such as the filamentous Spirogyra and the grasslike stoneworts. Most algae are planktons carried passively by water, although some macroalgae have holdfasts for anchorage.