William Brown. 
1 12 
Action of Extract on Plant Tissues. 
The method of experiment consisted simply in placing pieces 
of plant tissue in the extract. In the case of leaves and floral 
structures, it was found advisable to inject with the extract, as 
otherwise the action only proceeded slowly from the cut surface 
inwards (see later). Experiments in which the leaves, etc., were 
injected with water served to control such injurious effects as might 
be produced by the process of injection. 
In all cases the action of the extract was found to be of a 
two-fold nature: (1) An action upon the cell walls of the plant, 
resulting in the complete disorganisation of the cell wall structure, 
so that the cells separate readily from each other and the cellulose 
envelope of each individual cell becomes disintegrated ; (2) an action 
upon the living cell itself, resulting in its death. 
The former action is shown by the tissue losing its coherence. 
Thus after a short treatment (about half an hour) with the extract 
discs of potato or turnip tissue (^ mm. thick) readily fall to pieces 
on handling. A similar rotting effect is produced in the case of 
many foliar and floral structures. In the case of some petals the 
action is extremely rapid, the injected part becoming limp and 
obviously disorganised within a few minutes of injection. 
A method of quantitatively determining the activity of the 
extracts employed was elaborated, having as its basis the determin¬ 
ation of the time necessary for the decomposition of discs of tissue 
(potato, turnip) of standard thickness. 
The killing action of the extract is shown variously in different 
cases. In the case of coloured structures it is shown by the escape 
of the colouring substance from the cells on death. Thus petals of 
rose, Viola, Gloxinia, etc., on treatment with the extract rapidly 
become decolorised. In other cases death of the cells is shown by 
the development of a colouration which is held in abeyance as long 
as the cells are alive. Thus when leaves of broad bean are 
injected with extract, they rapidly become black; when lettuce 
leaves are similarly treated they become brown. These latter 
phenomena are due to oxidase reactions which are particular to the 
plants concerned and have no relation to the fungal extract as such. 
In the case of colourless tissues, the killing action of the extract can 
be followed by examining the relation of the affected cells to 
plasmolysis in hypertonic solutions. 
The action of the extract has been tested in this way on a 
