When tissue is held and allowed to rot spontaneously, the pulp is decomposed into a granular, watery mass. The cells beneath the epidermis are the finest and driest in the sound tomato, considerable pressure of the cover-glass being required to separate them for examination. Even when forced apart, the cells retain their shape. They contain a delicate semi-transparent protoplasm with a rather large nucleus surrounded by protoplasm and having strands from this mass connect with the protoplasm lining the wall. Pieces of the same tissue, on having the skin removed so as to expose the broken tissue to the air, were covered with mold in one day and in three days so badly disorganized that the cells separated with the weight of the cover-glass. The cells were transparent, the walls collapsed into a wrinkled mass, the protoplasm had disappeared, except a skeleton of the nucleus, but the red chromoplastic masses were intact. The middle lamella of the cells is the part which dissolves first, allowing the cells to separate and causing the walls to become thinner. The cell cavity is often filled with bacteria, so that the effect of the rotting can not be seen until the cells have been washed thoroughly. These bacteria have been mistaken for the particles left by the decomposition of the cell contents. The vascular bundles are surrounded usually by small parenchyma cells which do not separate readily from the strand in the healthy tissue, but in the decayed tissue the vessels can be seen clearly, free from other tissue. In advanced stages of rottenness the walls of the vessels may be dissolved, leaving only the spiral thickening, and the parenchyma tissue crumbled into powder-like fragments. The parts of the tomato which resist rotting the longest are the skin, which may be washed clean of adhering particles, the spirals of the vessels, and red particles of the chromoplasts. The conditions found in the rotted sections and pieces of tomato can be distinguished in the poor ketchup and these factors, together with the large number of organisms present, serve for purposes of differentiation. ORGANISMS IN KETCHUP.