Last Saturday, while I was out walking in the hills to the south of Glasgow, I collected a sample of water from a boggy area for Fred to examine under his microscope. The water looked like green soup.
Under the microscope, we found that it was full of desmids. These are single-celled green algae. They can be seen among the strands of a filamentous alga in this image.
Algae are primative plants and include the seaweeds.