Macro-algae are known as seaweed. There are thousands of different species of seaweed on this planet. There is a Matchcard worksheek on the parts of seaweed.
Macro-algae are multi-cellar organisms that range from several inches to several yards in height. They are benthos which are embedded to the ocean floor.
There is a small amount of differentiation of the cells in the different parts of the seaweed. For instance, the cells of the floats are slightly different from the cells in the blades or holdfasts. The amount of differentiation is significantly less than would be seen in plants and animals.
Learn more about the parts of seaweed.