Fern Life Cycle
All About The Fern Life Cycle
Instead of growing from seed, like your typical plant, the fern life cycle is quite different. The fern is a non-flowering, seedless plant. Instead of developing from a seed, the fern comes from a spore.
What we call branches and leaves on other plants, are called fronds on the fern. If you look in the underside of a frond, you can see where the fern life cycle begins. The little bumps you see are spore cases, containing the spores which are roughly equivalent to the seeds of other plants, although that is stretching things a bit. Gardeners growing ferns for the first time, will notice these spore cases, and wonder if the plant has become diseased, or infected with some type of weird insect. Those little bumps are quite normal.
Ferns will release spores from the spore cases to start a new generation of plants. A fern plant may release millions, and perhaps billions, of spores over its lifetime. To develop into a new plant, a single spore must land in exactly the right place, and under exactly the right conditions. Most do not. If you are a spore, your chances of enjoying a career as a fern are on the order of one in several million. You would think, given the characteristics of the fern life cycle, the plant should have become extinct a long time ago. In truth, the fern is one of the oldest of plant types on the planet, predating the dinosaur by at least a hundred million years.
If you should happen to be one of the lucky few spores, you will land on a spot with just the right amount of moisture and light. That will enable you, a single cell organism, to begin to divide and grow. After awhile, you'll become a little heart shaped plant, a prothallium. You would be flat and about 1/2 " across. Not very big, but considering you started as a single cell, this is really an awesome amount of growth. You're not however a fern, and actually never will be! What happens next, is you develop male and female sex organs on your underside. The female organ produces eggs, and the male organ produces spermatazoids. The spermatazoids swim through a droplet of water, to an egg, which it fertilizes. It is the fertilized egg from which the fern, called a sporophyte, will develop.
The truly unusual characteristic of the fern life cycle is that in going from the spore to a new fern plant, two different plants are involved. This is unlike metamorphosis, where one plant changes into another. The parent fern gives birth to the prothallium from its spore. The prothallium, not a fern, then gives birth to a fern plant (the sporophyte). It seems to be a round-about way of doing things, but for the fern, it has worked for hundreds of millions of years.
What you have read is typical of a fern life cycle, but to complicate matters even more, it should be mentioned that the fern has a couple of other approaches to propagating. In some cases, particularly in desert regions where water may be scarce, a sphorphyte can be produced without fertilization having taken place. This process is called apogamy. Ferns can also propagate by way of their rhizomes, which would be the only approach open to an infertile hybrid.
Not only do ferns normally propagate through a two step process, but these amazing plants even have a couple of back-up techniques. No wonder they're still around.