Linda Riddle, age 10, of Tulsa, Oklahoma, for her question:

Why does corn have silk?

Summer is the time for cooking freshly picked ears of corn. Each ear comes neatly sheathed in a husk of long green leaves and topped with a silken pony tail. When you peel away the leaves, you find that the threads of silk reach down to the golden kernels inside. They are there because they brought grains of pollen so that the kernels could become seeds.

Naturally a corn plant does its best to create seeds for the next generation. This job calls for two parent cells. One kind is in grains of pollen, the other kind is inside the corn kernels. The big problem is to get the two types of cells together to form fertilized seeds. Through weeks of sunshine and summer showers, the plant grows tall on its jointed stalk. Each joint sprouts a long; leaf that sheathes the stalk and then dangles down its pointed tip.

The top of the stalk sprouts a feathery tassel. It may be red or purple, yellow or green    but most corn plants wear pink tassels. Meantime stubby ears are sprouting down on the stalk. There may be as many as eight of them, each one tenderly tucked in the base of a leaf and tenderly wrapped in its own leafy husk. The pithy corncob is crowded with rows of young green kernels    and the kernels sprout long threads. These silky threads poke up and form the shaggy pony tail on top of the ear.

The pollen grains are in the tossing tassels. The egg cells are inside the young kernels. The job of getting them together is not easy because the kernels are tightly packaged in their leafy husks. When the pollen is ripe, the midsummer breezes blow clouds of its dusty grains around the corn fields. But without those silky pony tails it could never reach the kernels. When a pollen grain nets stuck on a thread of corn silk, it starts to grow a tiny tube. Down this tube moves the pollen’s parent cell to reach the other parent cell in the kernel. The two cells merge together and form a fertilized embryo. Now the kernel can ripen and become a seed.

After all this trouble, you would think that the plant could scatter its seeds for next year’s corn crop. Maybe the corn’s wild, weedy ancestors could do this. But our field grown corn has been cultivated for thousands of years. With all this pampering, its ears have grown crowded with fat kernels. When they fall to the ground, the seeds are too close together to get started and as a rule, their tangled roots strangle each other. So the seeds must be separated and planted by human hands.

Nowadays, most of the seeds are taken from hybrid corn. This special corn comes from super parent strains    and once again, human hands are needed to make it possible. The pollen is not allowed to blow around freely. Samples from one good strain are taken by hand and placed on the silky pony tails of another good strain. Then the fertilized ear is wrapped in a bag and left to ripen. In this way we get better and still better strains of hybrid corn.