rmaldehyde with
various tannic acids. Second, by various treatments of cork, decomposition
compounds showing tannin-like properties may be obtained.

Some investigators have held that not only cork tissue but also other
lignose, or cell-wall material, may be developed from tannins. Certain
observations with _Spirogyra_ seem to indicate that tannin may play an
important part in the formation of new cell walls during conjugation, as
cells which are ready to conjugate are rich in tannin, which gradually
diminishes in quantity until it is practically absent at the time of
spore-formation. There seems to be no evidence that tannins perform any
such function as this in higher plants, however.

Again, tannins may play a very important part in pigment-formation. They
are very similar in structure to the anthocyanin pigments, both being made
up of practically identical decomposition units, the phenolic bodies. The
disappearance of tannins during the process of ripening of fruits may be
connected, in part at least, with the development of the brilliant red,
blue, and yellow pigments which give such rich colors to the thoroughly
ripe fruits.

Finally, certain of the tannins undoubtedly serve as protective agents to
prevent the growth of parasitic fungi in fruits, etc. Recent investigations
show that at least some of the varieties of fruits which are resistant to
the attacks of certain parasitic diseases utilize tannins for this purpose.
This protective effect may be accomplished in two different ways. Either
the tannin actually serves as an antiseptic to prevent the growth of the
parasitic fungus within the tissues of the host plant, or it assists in the
development of a corky layer which "walls-off" the infected area and so
prevents further spread of the disease through the tissue. Examples of
both types of protective action have recently been reported.

It is obvious that the different forms of tannins may play different roles
in plant life, and the same tannin substance may possibly serve different
purposes under different conditions.

BIOLOGICAL SIGNIFICANCE OF TANNINS IN FRUITS

The presence of tannins in fruits and the changes which they undergo during
the ripening process cannot fail to attract attention to their biological
significance in serving to protect the fruit from premature consumption as
food by animals.

Tannins are of frequent occurrence in green fruits, imparting to them their
characteri