on Green Leaves and other Parts of Plants. 1 8 1 
In the case of the hair of the sepal of Aconitum , so little 
disturbance had taken place in the cell-sap, that, although 
anilophyll had crystallised out, in and on the shrunken proto- 
plasm, the cell-sap retained its purple colour almost un- 
changed. It seemed to us, that in every case examined 
under the microscope, it was some constituent or constituents 
of the protoplasm to which the reaction was due. From a 
chemical point of view, it is difficult to understand the 
rapidity with which the reaction takes place in the cell if 
active oxygen is not present at the same time. In the plant- 
cell the phenomena described may be frequently seen after a 
few moments and at the ordinary temperature, whereas in 
a laboratory-experiment, using aniline and hydrogen peroxide, 
the formation of anilophyll only takes place slowly, unless 
heat be applied at the same time. Hence it would follow, 
assuming that there is an activation of oxygen in the cell, 
that the process is more rapid when it passes through two 
distinct stages than when it passes through one only, which is 
hardly likely. 
It is not at all necessary to suppose that if active oxygen be 
present in most cells it should exist there in the form of hy- 
drogen peroxide or of ozone— indeed, it is highly probable that 
it is present in some other form. In the cases described by 
Pfeffer it is possible that there may have been active oxygen 
present, but of a kind not sufficiently potent to act on the 
chromogens or the colouring-matters of the cells, but still 
able to produce an oxidising effect on aniline. The intro- 
duction of hydrogen peroxide in the manner described by 
Pfeffer would then have induced changes which would not 
under ordinary circumstances have taken place. We may 
state in corroboration of this view that having treated the 
purple petals of Tradescantia — the staminal hairs with which 
some of Pfeffer’s experiments were made being too minute for 
our purpose — with aniline, we obtained by this means a quan- 
tity of anilophyll. We see no objection to the assumption 
that there are substances in the protoplasm — probably asso- 
ciated with specialised microsomata, etiolin and chlorophyll- 
