Shirley Bellenfant, age 11, of Nashville, enn., for her question:

What are algae?

Algae are simple plants, most of them living in the water. The sea moss and the sea lettuce are algae and so are all of the different kinds of sea weeds, from the tiny floaters too small for our eyes to see up to the long 600‑foot kelp. The green pond scum and many fresh water weeds are also algae. Certain pink algae live on the surface of snow and others team up with fungus plants to form lichens.

We say that algae are simple plants because they have no roots. Nor are they divided into leaves and stems as the higher plants are. True, some of the seaweeds look like leafy brunches. But each tendril does the work of leaves, roots and stems.

The long, trailing kelp clings to the ocean floor with a holdfast which you might mistake for a root. However, its only job is to keep the long tendrils from floating away. It does not take in moisture for the whole plant as a true root does.