The great green garps live in the deep forest. They usually like cool, moist places. But there are a few odd garps that can tolerate the bright sun and like to live on rocks. But most garps dry up and die when they get too hot. Every winter something interesting happens to garps. They sprout great big, hairy boils under their arms. These woolly growths don’t bother the garps. In fact it feels good when these boils finally pop and send little brown spores exploding into the air.

The spores are lightweight and fly high into the sky. When they fall back to earth most shrivel up and die. But a few find the perfect conditions, rotting leaves that are always moist and out of the sunlight. These spores sprout and begin to grow.

The spores grow into mini‑minis. A mini‑mini is smaller than a dime and very hard to find. The mini‑minis love the low light of winter and thrive in wet weather. After a heavy rain the mini‑ minis make special traveling cells. I call these tiny cells, the salesmen. These traveling salesmen swim away along the forest floor. They can swim because they have long tails that whip back and forth. By wiggling along they soon reach another mini‑mini. Each mini‑mini has a special side pocket and in each pocket is a single egg. One salesman prowls around until he finds the pocket and then dives headfirst right into the egg ‑‑ boom!

Now the egg in the mini‑mini sprouts and begins to grow into a garp! With the mini‑mini still clinging to its side the garp pokes its head out of the decaying leaves. Finally the mini‑mini dries up and falls off. Nothing but a great green garp is left.

I often tell this story to children and adults to help them understand the life cycle of a fern. Ferns peaked about 250 million years ago and have declined in recent eons. They are still widely distributed throughout the world and flourish in warm, moist environments. Some ferns tolerate deserts and others even survive under arctic conditions.

Ferns are one of the so‑called primitive plants, many of which exhibit an obvious “alternation of generations.” They have a life cycle consisting of two entirely separate plants that are often very different in size and shape. Ferns, algae, mosses, and horsetails all grow and reproduce this way.

In the story the great green garps are the familiar ferns‑‑ the large plants that you see growing in the forest or on a grassy hillside. Botanically the fern is the sporophyte generation because it produces the spores. Under the leaves (the arms) grow brown sori (the boils). The sori produce spores with only half the usual number of chromosomes‑‑haploid. When the sori ripen they explode and shoot the spores out into the air.

The spores require a moist area and the presence of blue light to grow. They develop into a tiny plant (the mini‑mini) only one centimeter wide. This is the gametophyte generation because it produces gametes (sperm and eggs). The tiny plants or gametophytes are hard to find, but by looking carefully underneath a large fern or on a moist slope you may discover one.

On the underside of the gametophyte there are two reproductive structures. One, the antheridium, produces flagellated sperm (the salesmen) and the other, the archegonium produces a receptacle (the side pocket) containing one egg. Both the egg and the sperm are haploid like the parent gametophyte.

The sperm swim through a fine film of water on the wet forest floor to the archegonium and fertilize the egg. The result is a zygote with a complete set of chromosomes‑‑diploid‑‑which is at first nourished by the tiny gametophyte. It matures into the familiar fern. Now we are back to the sporophyte generation, another great green garp. Got that? It’s complicated. That’s why I made up the story.

Here in the Bay area we have about about 25 species of ferns. To identify our native ferns use Pacific Coast Fern Finder by Keator and Atkinson.



Posted on

August 23, 2009