Denise Barbree, age 13, of Sarasota, Fla., for her question:

WHAT IS THE ORIGIN OF POPCORN?

Corn is one of the most valuable crops grown in the United States, and it is just possible that there are more types of corn grown than any other cultivated plant. Popcorn, sweet corn, flour corn, dent corn and flint corn are the five main kinds of corn harvested in this country, and each has it own characteristics and uses.

It is believed that all our modern corn types had a common ancestor called pod corn, but exactly where it was developed is still a mystery. Plant scientists agree, however, that it probably originated in northern South America, Central America or possibly Mexico more than 4,000 years ago.

Corn was strictly an Indian treat until Columbus discovered America. Centuries before his ships arrived from Spain, the Indians of both North and South America were using it as a main part of their diet. They were accomplished farmers, too. They knew how to fertilize their crops using fish, and they also practiced methods of crop rotation. Among the many types of corn they cultivated was a special variety that would burst into fluffy white blossoms when roasted  popcorn. Where and how the Indians discovered popcorn will probably remain a mystery forever. But the fact is, they did discover it.

You might think that corn is corn, but this is not so. Popcorn is different. If you were to take different kinds of corn, place the kernels in a frying pan and heat them to about 400 degrees F., popcorn would be the only one that would perform its inside out act. The other kernels would either crack or char. The reason for this is found in the popcorn kernel itself.

A popcorn kernel is somewhat smaller than other corn kernels.  It also has a much tougher covering. Inside the kernel is a moist, starchy mass. As the kernel is heated, the moisture changes to a gas which expands and finally causes the tough outer covering to burst with a loud pop. As it pops, the pure white pulp inside the kernel bursts forth and becomes true to¬ life popcorn  many times the size it was as a kernel. From a half cup of popcorn kernels, you can expect to get as much as a quart when it is popped.     

Popcorn is grown in much the same way as ordinary corn and even looks like other corn, except that its ears are somewhat smaller and the kernels are rather pointed. Rows of popcorn may be planted closer than rows of other varieties of corn, and farmers generally harvest their popcorn after the kernels have had a chance to dry out. Most of the popcorn produced in the United States is grown in Iowa, Indiana, Illinois and Ohio.