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.