Maureen Murphey, age 13, of Boise, Idaho, for her question.

What causes mildew?

A patch of mildew is made by little garbage ms n. They have their order from Mother Nature. Break down this and that into tiny fragments of rot and decay. Digest the fragments and turn them into simple chemicals. New plants need these chemicals to flourish and grow. New animals are waiting to feed on the growing plants. Without little garbage men such as the mildews life would come to a stop. There would be no decay to turn old stuff into new food supplies,

However, the mildews sometimes seem to take their work too seriously. They attack living plants and break down their tissues, Other mildews attack leather, wall paper and even the plaster. Still others specialize in disposing of linens and clothes.

All mildews are minute members of the plant world. They belong to the fungi family, cousins of the mushrooms. Those that feed on living plants are called parasites. Those that feed on dead stuff such as leather linen and paper are called saprophites.

Mildew will arrive when you leave a damp table cloth rolled up for a few days. When you open it, there are the patches of tell‑tale blueish green. Leave it longer, and the patches will crumble away with rot. The little garbage men are Just doing the job they were ordered to do.

How did they get inside the rolled‑up cloth? Mildews and their kin are spread spores. These are little seed bodies far smaller than the smallest speck of dust. They are everywhere adrift in the air, even over the vast ocean. The spores can start new plants and the plants can also multiply by cell division. No doubt the patch of mildew on the cloth was spread by using both methods.

The spores drift around the world for a long time, hoping to land in tht right growing conditions. They need moisture, damp air and not too much sunlight. Most of them perish. Some may have settled on the cloth, all ready and waiting.   They started sprouting 3in the damp, dark rolled up folds. They grew into pale meshes of threads called myceliumi.  The young patch of mildew looks white and fuzzy.

Then the mycelium sends up colored shoots, they may be spikes fronds or pom‑poms, Under the microscope they look like a garden. The patch of mildew turns blue‑green. The sprouts grow spore pods, They burst and launch trillions of new spores into the air:

All this time the linen cloth is rotting with delay; You can stop it once by exposing the little garbage men to sunshine and plenty of dry air. If the patch of mildew is still young, the sun may even bleach out the stair, When you know the needs and life story of the mildews you can save your books and clothes from attack. Store in dry air. From time to time, let in the sun and breezes to seldom used objects.