stic astringent taste. They nearly always disappear as the fruit
ripens. The fact that during the ripening process both sugars and fruit
esters, as well as attractive surface pigments, are developed has led
certain investigators to the conclusion that tannins serve as
mother-substances for these materials in the green fruits and are converted
into these attractive agencies during ripening. There is nothing in the
chemical composition of tannins which indicates, however, that they are
precursors of sugars or fruit esters, although (as has been pointed out)
they may give rise to anthocyan pigments.

Further, recent researches concerning the tannin of persimmons (the
best-known and most striking example of the phenomena under discussion)
clearly show that the tannin is not actually used up during the ripening
process; that instead it remains in the ripe fruit in practically
undiminished quantity; but that when the fruit is ripe, the tannin is
enclosed in certain special large cells or sacs, which are surrounded by an
insoluble membrane, so that when the fruit is eaten by animals the
astringent tannin, enveloped in these insoluble sacs, passes by the organs
of taste of the animal without causing any disagreeable effects. This
walling-off of the astringent tannins can be stimulated in partially ripe
fruits by treating them with several different chemical agents, the
simplest method being that of placing the unripe fruit in an atmosphere of
carbon dioxide gas for a short period. The artificial "processing" of
persimmons to render them edible for a longer period before they become
naturally fully ripe and subject to decay is now a commercial enterprise.
This process is of interest because of its possible connection with the
conversion of tannins into cork, under the influence of carbon dioxide gas,
as mentioned in a preceding paragraph.

From these facts, it is apparent that in persimmons, and probably in other
tannin-containing fruits, the process of natural selection has developed a
mechanism for the secretion of tannin in green fruits, followed by a
process for walling it off in harmless condition when the fruit is ripe,
which serves most admirably to protect the fruit from consumption by
animals before the enclosed seeds have fully developed their reproductive
powers.

REFERENCES.

ABDERHALDEN, E.--"Biochemisches Handlexikon, Band 7, Gerbstoffe,
Flechtenstoffe, Saponine, Bitterstoffe, T