Stephen Guth, age 12, of Allentown, Pennsylvania, for his question:

What are hybrid plants?

There are signs that the next page of history will turn us to a green world, in which people will pay proper respect to the earth and its generous plants. One of these happy signs is a bursting new inerest in hybrids. These are superior new plants created by man and nature, working together. For example, nature created the modest little wild rose. From this, mankind developed all those huge, showy hybrid roses.

All our foods come from either plants, or animals that feed on plants. The plant world stands between us and starvation and the merciless famines of past history struck when the crops failed. When wandering hunters settled to form the first civilized communities, the first order of business was farming.

The first farmers cultivated seeds from wild plants. They learned to select seeds from superior plants to develop better strains. This selective breeding worked because plants as well as animals tend to inherit the genetic qualities of their parents. After uncountable generations, this patient process developed worthwhile cereals from stringy wild grasses. A breakthrough occurred in the 1690s, when botanists discovered that seeds form from male and female plant cells.

Experiments proved that sex cells from different plant varieties can be united artificially. Superior varieties were crossbred and time after time the seeds inherited the superior qualities of both parents. In modern horticulture, this is called hybridization.

One of the best examples is the corn that feeds us, our beef and our dairy cattle. The best hybrid seed corn is produced by inbreeding and crossbreeding several strains through several generations. Let's say that pollen from tassels on variety A is transferred to the silk of variety B. In the same manner, variety C is inbred with variety D. The seeds produce two single cross hybrids, AB and CD. Next year, the two single crosses can be crossed. Our best hybrid corn seeds are double crosses of this sort.

Crossbreeding was used to produce more than 8,000 hybrid garden roses from a few wild rose plants. Every year, the array of hybrid flowers and vegetables become ever more amazing. Old strains are crossbred to give us new types that survive severe weather and resist many old plant diseases.

Plants grown from hybrid seeds tend to he vigorous growers and high yielders. However, their seeds result from careful crossbreeding of their sex cells, which is controlled artificially. When hybrid plants are given their freedom, they tend to change the rules. Some hybrids produce no fertile seeds. Others do, but the plants from the next generation rarely inherit the qualities of their hybrid parents.