Handbook of Nature-Study · Lesson CXXXIII · Topic 20: Summer wildflowers, climbers and water plants
133. Pondweed
Goal: Your child looks at a pondweed in a basin of pond water and explains how a plant that lives under water is built differently from a land plant.
You'll need
- Nature notebook, pencil and colored pencils
- A hand lens (magnifying glass)
- A clear bowl or white basin
- Pond water
What's in the book
A Teacher's Story about pondweed, with a drawing of its small flowers, and the lesson: Leading thought, Method and seven questions. (In the scan's text the lesson heading is misprinted, but the lesson is on this page.)
The lesson, step by step
When and where
Pondweeds grow under the surface of ponds and slow streams. Comstock says to study them in spring or fall and to watch the blooming in late July. Any kind of pondweed will do.
Water safety: an adult stays right beside children at any pond or stream. Stay on the bank, a dock or solid ground; pond bottoms are soft and can be deeper than they look.
The leading thought
The pondweed lives entirely below the water; at blossom time, however, it sends up its flower stems to the surface of the water, and there sheds its pollen, thus securing cross-pollenation.
Where does it grow?
Where is the pondweed found? Does it ever grow out of water? Does it ever grow in very deep water? Does it ever grow in swiftly flowing water?
In the basin
An adult lifts out one sprig from the edge of the pond and floats it in a basin of pond water.
Break off a plant, does it float? Do you think it would float off and die, if it was not anchored by its root?
Compare the stem of pondweed with that of any land plant standing straight. What is the chief difference? Why does the pondweed not need a stiff stem to hold it up?
Leaves
Examine the leaves. Are all of them below the surface of the water?
Lift a stem out of the water and watch it flop. Then put it back. Water holds it up.
Blossom time
Have you ever noticed the pondweed in blossom? How does the blossom look on the water? Can you see the white pollen floating on the surface of the water?
Nature notebook
Draw a land plant and a pondweed side by side and label how they differ: stiff stem or limp stem, thick leaves or thin. Return the pondweed to the same pond, and don't carry water plants from one pond to another. Wash hands when you come in.
Answers to the book's problems
The pondweed does not need a stiff stem because the water holds it up. Its roots mainly anchor it; the water around the leaves supplies water directly.
Worked out for this site from the scan. If a number in your copy differs, trust the book.