When bread is several days old, you sometimes find little patches of green or gray mold on it. The mold is really a patch of tiny, tiny plants, which grow like weeds in a garden. Weeds grow wild. Nobody plants them in a garden.
Nobody plants mold either. Where does mold come from? It comes from little specks that float around in the air — specks so small that you can't see them. When the specks land on a piece of moist bread in a warm room, they begin to grow. just as seeds grow in warm, moist soil. The tiny mold plants are shaped like flowers, but they are not really flowers. When they have grown, they send out more little specks into the air and onto the bread. The specks are called spores and they are like seeds.
Sometimes mold spores fall onto very dry bread in a very dry room. Then they can't grow. They need moisture, just as all plants do.
Mold grows on other things beside bread. It grows on meat and on vegetables stored in damp places. It grows on the top of home-canned foods that haven't been closed up tight. It can even grow on shoes and clothes and books in damp closets.
