Fungi vary in size from microscopic plants to larger forms such as mushrooms; molds are a common form of microscopic fungus that cannot make their own food (they do not contain cholorophyll).

Place a piece of white bread in each of two coffee cans. Moisten the bread in one can but not in the other. Leave both cans uncovered for three hours, then cover them, and place them in a warm, dark place for a week. Compare the growth of molds on each piece of bread.

You will find that the dry bread shows much less growth than the moistened bread. You will conclude that moisture is important for the growth of molds. You can try this again, using different kinds of breads, such as home made (without preservatives), rye, cinnamon, etc.

What would happen if you moistened the bread with alcohol? What if you moistened it with jam? What if you put a third coffee can culture into the fridge?

There are many kitchen scientists who conduct experiements on molds in the refrigerator. Many fridges contain little dabs of once-edible substances that become unidentifiable. Molds grow in many different colors and shapes, depending on their media. Molds that grow on rhubarb pie, given enough time, look like pink fir trees. Celery, if left in a bag long enough (maybe a couple months), liquifies, then grows flat, pink mold. I have discovered these facts by running many refrigerator experiments, purely in the interest of science.

There are two requisites for refrigerator experiments:

(1) The substance on which mold will grow must have been edible before it was saved.

(2) The substance which will become a culture medium must be in a container that can be tightly closed. We do not want fungi or bacteria floating freely around the fridge, flavoring the butter, and doing other bad things.

There are more than eighty-five thousand known kinds of fungi.

Some are beneficial in the manufacturing of beverages and cheese and in the production of penicillin. Some are a nuisance, such as those that grow on leather; others are
harmful and cause disease in plants (mildew on grapes, rot on Peaches) or on people (ringworm, athlete's foot).

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Place two drops each of different milk products (such as cottage cheese, half-and-half, ice cream, or buttermilk) in different petri dishes. Make three sets, and place one in a refrigerator, one in a hot place, and leave one at room temperature. After two days, smell them and observe samples under a microscope. You will note marked differences in the products kept in a refrigerator.