Jan Hulsey, age 14, of Avondale Est., Georgia, for her question:

What are gymnosperms?

This topic introduces us to the classifications of the plant world. More than 300,000 species are known and some experts suspect that the total plant kingdom may include half a million different species. The known species are classed in mayor divisions, which are subdivided into smaller and smaller related groups. About 500 plants are rated as gymnosperms because of their special seeds.

In the plant world, success depends upon the development of seeds, plus their protection and dispersal. The first and the simplest plants belonged to the sea, perhaps two billion years ago. Perhaps 420 million years ago, some of them managed to survive on the land. These became club mosses, ferns and horsetails that multiplied by casting countless minuscule spores on the breezes.

Seeds were invented more than 300 million years ago    and for ages all of the seed bearing plants were gymnosperms. This botanical term merely means "naked¬seed" plants. A good example of a gymnosperm is a cone bearing Christmas tree. This method of seed production, protection and dispersal was so successful that the conifers have changed very little.

A conifer bears male cones that produce pollen and larger cones that produce female cells. Fertilization depends on the wind to disperse clouds of pollen. A few grains reach and fertilize female cones. The conifer is called a gymnosperm because the naked seeds are exposed on the inside of the scales that form these cones. When the seeds are ripe, the cone turns upside down and they fall to the ground where a few may establish new trees.

Some 500 of the original gymnosperm species have survived to modern times, with few changes. However, the best was yet to come. Anew breed called the angiosperms arrived, bringing all the flowering plants, trees and shrubs that now adorn the earth. The term angiosperm means "covered seeds." It refers to seeds that are protected inside pods, cases or fruits. The first of their kind arrived about 150 million years ago.

The earlier, and still successful gymosperms rely on the breezes to fertilize their naked seeds. However, this is risky and clouds of pollen are wasted. The flowers of most angiosperms bear both male and female cells. This is less risky and more economical.

Of the 500 surviving gymnosperms, about 350 are cone bearing trees and shrubs. The 150,000 or so angiosperms account for about half of the modern plant species. They rely more on insects to pollinate their seeds and most insects are attracted to pretty colors and sweet perfumes. This, of course, explains why the angiosperms display their seed cells in flowery, fragrant blossoms.