Plant Diseases 
349 
Bacteria, however, when they get inside the host plant, 
are able to live and multiply in unlimited numbers without 
ever coming to the surface at all. At present there is no 
known cure for such diseases. The only thing to be done 
is to burn any diseased plants, being careful to destroy 
every part of them and thus prevent any further attack. 
No part of them should be used for propagating pur- 
poses, and every effort should be made to destroy in- 
sects that have fed on them, lest they go to healthy 
ones, carrying the bacteria with them, and in this manner 
inoculating those plants that were previously free from 
the disease. 
The epidermis of plants, like our own skin, is proof 
against the attack of disease germs, but when once the 
epidermis is broken the tissue is laid bare to the attack 
of these organisms. When once the bacteria get inside 
the tissue, they begin to feed on the contents of the cells. 
Not only do they feed on the cell substances, but they 
set up changes in these substances which are highly 
injurious to the plants, and which to a great extent bring 
about their destruction. Some diseases produce similar 
effects in animals and men. The germs (bacteria) pro- 
duce a toxin which is the direct cause of the disease. 
Fo counteract this, science produces an antitoxin, which, 
if successful in its action, cures the patient, but if not, is 
fatal. Hence for such diseases in plants we must try 
to find an antitoxin which will destroy the disease from 
within, as the application of fungicides from without has 
practically no effect on these bacterial diseases. It would 
be just as absurd to expect to cure a person suffering 
from typhoid fever by washing him with disinfectants, as 
