waxes and lipoids have a harder consistency than fats: but this
is not always the case, since "wool-fat" and spermaceti, both of which are
true waxes in composition, are so nearly liquid in form as to be commonly
called fats; while certain true fats, like "Japan wax," are so hard as to
be commonly designated as waxes. It is plain that physical properties alone
cannot be relied upon in the classification of these bodies. In fact, there
is no single definite property by which members of this group can be
accurately identified. There are many other types of substances belonging
to entirely different chemical groups, which have oily, or fat-like,
properties.

A. FATS AND OILS

OCCURRENCE

Fats and oils are widely distributed in plants. They occur very commonly in
the reproductive organs, both spores and seeds, as reserve food material.
In fungi, oils are often found in the spores, but sometimes also in
sclerotia, mycelia, or filaments. For example, the sclerotia of ergot have
been found to contain as much as 60 per cent of oil. In higher plants, many
seeds contain high percentages of oil, so as to make them commercial
sources for edible or lubricating oils, such as olive oil, rape-seed oil,
cottonseed oil, castor oil, corn oil, sunflower-seed oil, etc., etc. Nuts
often contain large proportions of oil, the kernel of the Brazil nut, for
example, sometimes contains as high as 70 per cent of oil, while an oil
content of 50 per cent, or more, is common in almonds, walnuts, etc.

Oils also occur as reserve food material in other storage organs of plants,
such as the tubers of certain flowering plants, and the roots of many
species of orchids. Sometimes the appearance of oils in the stems of trees,
or the winter leaves of evergreens, seems to be only temporary and to occur
only during periods of very low temperatures.

Much less frequently, fats or oils are found in the vegetative organs of
plants, as in the leaves of evergreens. Their appearance and functions in
these organs seem to be much less certain than in the other cases cited
above; although in rare cases a considerable proportion of oily material
has been found to exist in definite association with the chloroplasts.

The vegetable fats and oils have many important industrial uses. Some of
them, such as olive oil, cottonseed oil, cocoanut oil, etc., are largely
used as human food. Others, as castor oil, ar