Each kind of organism, whether bacteria, yeast, or mold, is adapted to a certain type of food material, and is generally found assoc1ated it. Yeasts may be present in foods containing sugar; molds occur upon many fruits and upon their products, and are Instrumental in the spoiling of starchy foods, as bread. Bacteria are abundant in most foods, but they grow best on those con taining protein substances, as peas, beans, and meat. Some bac teria change into specialized forms fitted to reproduce the species after a period unfavorable to their growth. These resistant forms are called spores. Vegetables are much more difficult to preserve than fruits, as they are ordinarily infected with these spore-bearing bacteria which are capable of withstanding high temperatures. Yeasts and molds, on the other hand, are easily killed by heat. The whole problem, then, of food preservation, including can ning, storing, and drying, involves the destruction of undesirable organisms and the prevention of their growth.