Marlis Falls, age 13, of Bessemer City, N.C., for her question:

What are gymnosperms?

The word gymnosperm belongs to the plant world. It is a scientific term coined from two Greek words meaning naked and seed. The notion of a naked seed seems rather odd  until you realize that most seeds are encased in durable or fairly durable shells. The plants that bear these protected seeds are called angiosperms. And compared with the ancient gymnosperms, they are newcomers in the world.

Nowadays the plant world thrives throughout the global ocean and spreads green cloaks embroidered with flowers over much of the land. The whole beauteous miracle began perhaps 3 billion years ago, when the first simple plants arrived in the ancient seas. They were alga types, not unlike some of the simple algae that still thrive in the salt and fresh waters of the world.

Some of the simplest models multiplied by dividing their single cells into pairs of identical twins. In other cases, a few cells broke loose from their parents and grew into new plants. For millions and millions of years, the plant world knew only these and perhaps a few other simplified ways to reproduce.

Then as now, the tides tossed uncountable algae to dry and die on the beaches. Then as now, a few hardy specimens overcame this hardship and used it to advance one giant step in the fabulous story of life on earth. Early in the Paleozoic Era, some 438 million years ago, some of these hardy specimens had left their ancient cradle, the sea, and adapted to cope with life on the dry land. They were simple psilophytes, or bare plants, with creeping stems and upright branches.

Simple they were, but their future was boundless. A hundred million years later, as the Paleozoic Era drew to a close, vast areas of the land were clothed with forests of mosses and club mosses, giant ferns and horsetails. This was the thriving vegetation of the Carboniferous Period, which later formed our buried beds of precious coal.

Among this assortment of weird and wondrous vegetation appeared the first gymnosperms  or naked seed plants. They were cone bearing trees, the original ancestors of our handsome Christmas trees. In the Mesozoic Era, some 225 million years ago, the early dinosaurs lumbered through gymnosperm forests of cycads, ginkgoes and conifers. All of these trees produced naked seeds, unprotected by shells or outer cases.

For the next hundred million years or so, the gymnosperms were the most advanced members of the plant world. Then the earth gave birth to her first flowering plants  the angiosperms that bore seeds encased in protective coats. They included magnolias and maples and the ancestors of most of our modern non cone bearing trees. For more than 60 million years, the gymnosperms and the angiosperms have peaceably shared plains, valleys and slopes, adding their cones and their flowers to the beauteous plant world.

Our 500 or so gymnosperms are woody trees—including the largest and oldest redwoods. Most of them are pines and other cone bearers. The typical gymnosperm depends upon the breezes to spread its pollen, and its naked seeds are folded within the woody scales of a cone which enfolds and protects the developing seeds. After perhaps a year or more, the woody scales open and the ripe seeds fall to the ground.