Yeasts are the principal gas-forming agents in the fermentation of pulp. In the production of this gas they consume the natural sugar of the tomato. They will multiply by the budding method described above as long as they are in a medium which is favorable for their growth. As soon as this medium drys up, or for some other reason becomes an unfavorable medium for the multiplication of the yeast cells, the yeasts resort to spore forming, just as bacteria do. These spores are formed within the yeast cell, and when the cell wall breaks the spores pass off into the air. Like all other spores, they have a high resistance, and will float around in the dry state and remain alive for a very long time. When they light upon a medium in which they can grow they reproduce the yeast species, in the same manner in which the bacteria spore reproduces the bacteria species from which it was derived. Spores The spores, then, which are found in tomato products are of three different kinds, namely, mold spores, yeast spores, and bacteria spores. The greater number are almost always mold spores, since the mold plant produces spores under all conditions, while yeasts and bacteria only produce them under unfavorable conditions. When microscopical analyses of tomato products are reported, the mold spores and yeast spores are included with the yeasts in the term “Yeasts and Spores.” This is because a large number of the spores are very similar to yeast cells in appearance, and as it would be a laborious process for the analyst to separate them, the yeasts and spores are included in one figure, which greatly simplifies the analysis. The bacteria spores are not included in the count of “Yeasts and Spores.” How Germs Retard Their Own Growth