176. The fruiting of the fern

The lesson, step by step

1. When and where

   Go in summer. The book says July is best, or begin in June when the fruit dots are green and finish in September. Look in shady woods, along damp ravines and at the edges of wet meadows.

   Turn fern fronds over gently. You are looking for brown or green dots, lines or cups on the back. Pick only one or two fronds, from a place with plenty of ferns.

2. The leading thought

   Read it aloud, or tell it in your own words:

   Ferns do not have flowers, but they produce spores. Spores are not seeds; but they grow into something which may be compared to a true seed, and this in turn develops into young ferns.

3. Make a spore print

   Start this first, because it takes a day or two. The book says:

   Take a fern that is in fruit; lay it on a sheet of white paper and leave it thus for a day or two, where it will not be disturbed and where there is no draught; then take it up carefully; the form of the fern will be outlined in dust. What is this dust?

   Set it on a shelf away from fans and open windows.

4. Look through the lens

   Hold a fruit dot under the hand lens. Ask:

   Can you see with a lens many little, brown globules?

   Can you see that some of them are torn open? These are the spore-cases, called sporangia, each globule being packed with spores.

   Can you see how the sporangia are fastened to the leaf by little stems?

5. Who is this fern? The blanket key

   Young spore-cases are covered by a tiny "spore-blanket," the indusium. The book uses its shape as a key. Read these and see which one matches your fern:

   if it is cup-shaped, it is a boulder fern; if it breaks open and lays back in star shape, it is a woodsia; if the edge of the fern leaf is folded over all along its margin to protect the spore-cases, it is a bracken; if the tips of the scallops of the leaf be delicately folded over to make a spore blanket, it is the maidenhair.

   The full key on the book page also has the Christmas fern, the wood ferns, chain ferns, spleenworts and bladder ferns.

6. Ferns that change their leaves

   Some ferns grow special fronds just for spores. If you find a sensitive, cinnamon, ostrich or interrupted fern, put a spore frond beside a green one.

   compare carefully the fruiting with the sterile fronds, and note in each case the resemblance in branching and in pinnules

   Ask your child: Do they branch the same way, even though one looks withered?

7. What we know now

   The book hints that a spore grows into "something which may be compared to a true seed." Today we know the spore grows into a tiny, flat, green heart-shaped plant, smaller than a fingernail, on damp soil. That little plant makes egg and sperm cells, and a new fern grows from it. Look for pictures of a "fern prothallus."

8. Nature notebook

   Draw one frond and, beside it, one fruit dot as it looks through the lens. When the spore print is ready, add it to the page (an adult can spray it lightly with hairspray so it does not smear), and write the date and place.