OF VARIOUS KINDS OF TEA. 
19 
fine flavour and favourite tint. As already mentioned, the 
leaves when once sufficiently steamed do not undergo fermenta¬ 
tion, hence it is probable that this is caused by an organism or 
the like adhering to the surface of the leaves. For putt¬ 
ing this supposition into an experimental base, a certain 
quantity of the leaves was sufficiently steamed and allowed to 
ferment. It was found that the leaves did not suffer any visible 
alteration after one hour’s exposure to sun-shine, while in a 
parallel trial sun-withered leaves acquired the characteristic 
brown tint after the same interval. This alteration of colour can, 
however, not be taken as a decisive proof of the setting in of 
fermentation, since most of the chlorophyll may have been 
decomposed by a long action of steam, and since the decomposi¬ 
tion product or products may be more indifferent than 
chlorophyll itself, which may produce brown colouring matter 
in combination with organic acids or substances of an acid 
nature ready formed in the leaves or formed by the act of fer¬ 
mentation. It is a well known fact that an addition of a little 
acetic, citric, tartaric, or malic acid, or even of an acid salt, 
to an alcoholic solution of chlorophyll produces a yellowish 
green or brownish green colour. In the case of leaves rich in 
tannin as tea leaves the presence of any other acid is not neces¬ 
sary for the formation of a brown colouring matter, since tannin 
itself acts upon chlorophyll in a similar way as all other acids. 
According to the observation of Wiesner, a concentrated 
alcoholic solution of chlorophyll assumes a greenish brown 
colour, when mixed with much tannin, and the mixture throws 
down a dirty brownish precipitate when exposed to the air in a 
shallow basin. This brown substance is regarded as a com¬ 
pound of tannin with oxydized chlorophyll. C. Kraus assumes 
that a brownish black colouration in the dead leaves rich in 
tannin may be dependent upon a direct action of tannin upon 
chlorophyll. It is, however, only after the death of the cells 
that such an alteration in colour takes place, since chlorophyll 
granules, so long as the cells are living, are enveloped with liv¬ 
ing protoplasm which is impermeable to numerous substances, 
