Linda Harvard, age 8, of Dallas, Texas, for her question:

How do they make yeast?

If we had no yeast, our bread would be flat and heavy. It is yeast that fills a loaf full of spongy holes and makes the bread light. The yeast was made in a huge tub, and it was made from other yeast. For the wonderful stuff is alive and all living things must come from parents just like themselves. The pale powdery yeast is made from tiny little plants    though each single plant is too small for our eyes to see.

These tiny plants use up food and they multiply. When they have all the things they need, they multiply at a great rate. They like a big tub full of warm broth mixed with sugars and other chemicals. If we add, say, a cupful of yeast plants to the right broth, they begin to grow. Each little sausage shaped plant grows a bud. In about an hour, the bud is a new yeast plant, just like its mother. The cup of yeast we put into the tub has

multiplied to two cups. Then the mother and daughter plants grow buds and the buds become more yeast plants. After awhile, our first tap of yeast multiplies to 20 cups, 50 cups and maybe 100 cups. This is how they make yeast and more yeast for our daily bread.