Housekeepers spend a great deal of time dusting. Dust settles from the air and may make a gray coating over everything in a house.
   How surprised many housekeepers would be if they knew that part of the dust they wipe off the floors and furniture each day is alive! But it is. Dust is made up partly of tiny bits of rock. It may have in it bits of dead wood and dried leaves. It may have in it ashes from volcanoes— ashes from volcanoes have been blown clear around the world. It may have in it, too, particles left when a shooting star burned up on its way to the ground. It is almost sure to have some soot in it. But it also has in it yeasts and bacteria, and perhaps spores from several kinds of plants, and pollen from flowers. These are alive!
   Yeasts are very tiny microorganisms. They are much too small to be seen without a microscope. Bacteria are tiny organisms which are even smaller than yeasts. Some of them are disease germs. Mushrooms and molds and ferns are three of the kinds of fungi organisms that have spores. These fungi do not have seeds. They are scattered by spores instead. Pollen is the powder in flowers that helps form seeds.
   In a region where there has not been enough rain, there may be great dust storms. The dust blown about in these storms is mostly topsoil.