Karen Hayes, age 12, of Wichita, Kan., for her question:
HOW ARE MOSSES FORMED?
Mosses are living plants, and all living things emerge from other living things. Cats have kittens, chickens lay eggs. Next year's peas grow from the year's peas in the pod. A mighty oak tree grows from a little brown acorn. So we can be sure that new mosses are started on their way by parent mosses.
Our beauteous planet is clothed with more than 335,000 different plants. At least half of them bear flowers that add touches of embroidery to the green background. The mosses add a variety of velvety greens to the world's wardrobe ¬but no flowers.
There are about 14,000 different mosses, and back in the Paleozoic Era they were among the earliest plants in the world. This was some 350 million years ago. It was long before the plant world had developed seeds like peas and acorns.
However, the mosses thrived and multiplied, just as they do today. And since the ancient method of multiplication was successful, there was no reason to change it. Bascially, a new moss plant forms in two rather complicated stages. Its modern botanical name is alternation of generations.
Stage one begins when the parent mosses produce their sex cells. A moss plant may produce either male or female or both. The male cells are formed in groups; the females are singles. On some misty morning, when the world is damp with dew, the male cells break loose and slither around through the moisture. Here and there a lucky one meets and fertilizes a female egg cell, which stays on the parent plant and begins to grow.
However, this fertilized egg is not a seed. It produces a slender stem, topped with a capsule of tiny spores. Stage two begins when the capsule bursts and the ripe spores blow away with the breezes. Here and there a lucky one lands on a suitable spot. It spreads branches of green threads over the soil and becomes a protonema.
The threads have special joints that send down rootlets and each clump of rootlets forms a new moss plant.
A whole crowd of new moss plants may sprout from a single protonema covering the ground with a thick velvety carpet. When these plants mature, they will produce batches of male and female sex cells. A few fertilized eggs will stay with the parent plant, while they produce capsules of spores to be strewn on the winds.