Richard Dufour, age 13, of West Warwick, Rhode Island, for his question:

When was chewing gum invented?

People are born chewers, and exercising the chompers before, during and after meals is as old as human history. Our various ancestors chewed twigs and sticks, gummy rosins and a long list of other suitable substances that happened to be handy.

All our tasty treats are donated by the plant world. The long list includes sugars and sweet syrups, chocolate and vanilla, fragrant spices and minty herbs, Many of these tasty touches are added to our modern chewing gums    but the plant world also contributes the main ingredient: for the basic recipe. This durable gum is chicle, and its chewable qualities were discovered ages ago in Central America. Long before Columbus arrived, the people there extracted chewy chicle gum from their native sapodilla trees.

Sooner or later, the excellent qualities of chicle were bound to be discovered by other peoples. Its global tour began about a century ago, when the Mexican dictator, Santa Anna, visited New York, toting some of his native chicle gum in his baggage. It was a tasteless, doughy gum, but the New Yorkers who got a chance to sample it wanted more. One of these was an inventor named Thomas Adams. It is reported that he preferred his own rubber chewing gum. But he boiled up some of the new chicle and sold chewy bits in his store. His customers liked it.

This was about 100 years ago, and even without flavoring, gobs of chicle gum became very popular. About ten years later, the Adams recipe was improved by John Colgan of St. Louis. John thought he could sell more chicle gum in his drugstore if it tasted better, and he was right. He added some tangy, long lasting balsam flavoring to the chicle, and his customers loved it. Chicle is still the basic ingredient in our chewing gum    and the first flavored recipe was invented in St. Louis about 90 years ago.

A good thing is sure to be improved, and naturally all sorts of improvements were added to the original chicle gum recipes. Nowadays, about a quarter of the basic recipe is chewable chicle and about half is sweet, pasty caramel. Other ingredients include additives to preserve the recipe and selections from a long list of tasty flavorings.

The native Central American sapodilla tree is a large, handsome evergreen. It now grows also in the West Indies and the Philippines. Its sap is a rubbery latex, too thin to chew. Gashes are made in the thick brown trunk and liquid chicle drains into canvas bags. It is boiled until about a third of the moisture evaporates, leaving a gummy dough that becomes chewing gum.