Lesson CLXXXI

Bracket Fungi

Leading thought—The fungi which we see growing shelflike from trees, are deadly enemies to the trees. Their spores germinate and penetrate at some open wound and the growing fungus weakens the wood.

Method—It is desirable that a tree on which shelf fungus grows should be studied by the class, for this is a lesson on the care of trees. After this lesson the fungus itself may be studied at leisure in the schoolroom.

Observations—1. On what kind of a tree is the bracket fungus growing? Is it alive or dead? If living, does it look vigorous or is it decaying?

2. Is the fungus bracket growing against the side of the tree, or does it stand out on a stem?

3. Look at the place where the bracket joined the tree. Does it seem to be a part of the wood?

4. What color is the fungus on its upper surface? How large is it? How thick near the tree? How thick at the edge? Can you detect concentric layers or rings? If it is the large species used for etching, cut down through it with a knife or hatchet and count the layers; this should show its age.

5. Look at the lower surface. How does it appear to the naked eye? If you scratch it with a pin or knife does the bruise show? Examine the surface with a lens and describe what you see. Cut or break the fungus and note that each of these holes is an opening to a little tube. In each of these tubes spores are borne.

6. Have you ever seen toadstools that, instead of having the leaflike gills, have beneath the cap a porous surface like a little honeycomb or like the under side of the shelf fungi?

7. How many kinds of shelf fungi can you find? Which of them is on living trees, and which on stumps or dead wood?

8. If the fungus is on a living tree, then the tree is ruined, for the fungus threads have worked through it and weakened it so that it will break easily and is of no use as lumber. There must have been an open wound in the tree where the fungus entered; see whether you can find this wound. There must also have been a wound where the shelf grew out; see whether you can detect it. If the tree should heal all its wounds after the fungus entered, what would become of the fungus?

9. What does the shelf fungus feed on? What part of it corresponds to the roots and leaves of other plants? What part may be compared to the flowering and fruiting parts of plants?

10. What treatment must we give trees to keep them free from this enemy?