The term Algae is used for many often unrelated organisms with plant-like characteristics. In fresh water most of these groups can be found. Some live submerged, others form floating beds. The gutweed Enteromorpha intestinalis is an example of a species that forms what is often called 'pond scum'. Gutweed is a chlorophyte, a unicellular green alga. It forms macroscopic tubular colonies.

Part of the Collection of the Algae Archive of the Micropolitan Museum © Wim van Egmond