Welcome to You Ask Andy

Steve Carlson, age 13, of Costa Mesa, Calif., for his question:

 I NEVER SEE FERNS WITH FLOWERS. HOW DO THEY REPRODUCE?


Our beautiful planet has more than 350,000 different plants to clothe herself in. More than half of them bear flowers

that add vivid colors to the delicate greens of the landscape. Most flowers produce seeds for the next generation of plants, but the ferns have a very different system. They have no flowers because they get along quite well without them.

 

The lovely lacy ferns were among the earth's earliest forms of plant life. They were here long before the flowering plants arrived with their simplified method of reproduction by seeds. The fern's method of reproduction, a bit more complicated, is called alternation of generation  which means that the life cycle involves two steps and two different plant forms.

Most ferns live quiet lives in moist, shady woods. Their feathery leaves, called fronds, sometimes grow to as much as six feet in length. The young fronds start as thick stems with gracefully coiled tops. As the fronds grow, they uncoil and spread out to expose their lacy green designs. When the time for multiplying comes, the story begins on the underside of the mature fronds.

At the proper time spore cases form on the underside of the leaves in neat rows of small brown dots. When the spores are ripe, the coverings burst and the tiny spores are scattered by the winds. This stage of the life cycle is called the sporophyte generation.

The second stage of the reproductive cycle begins when a spore lands in just the right place for growth  a shady, moist spot on the forest floor. It sends down threadlike roots to soak up moisture and soon develops into a tiny heart shaped plant about the size of a dime. This plant is called a prothallus and begins the gametophyte generation.

On the underside of the prothallus, male and female cells develop. On a mild morning when the forest is damp with dew, the male cells break free and glide through the moisture. One of the male cells will unite with a female cell to produce a fertilized egg cell. This completes the gametophyte generation. The fertile egg cell grows by dividing itself again and again, and in time will begin sending out its own lacy fronds  a perfect copy of the original parent fern.

There are some 10,000 different kinds of ferns, and about 300 of these grow in the United States. They range in size from very small to super large. The tiniest are no larger than wee moss plants while tropical giants may reach up to 40 feet. Each is a bit different, but they all go through the same process of reproduction  one that has been successful for more than 200 million years.

 

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