82 PLANT LIFE ON THE FARM. 
thrown on the existence of any direct connection between 
the absorption of oxygen and the emission of carbonic 
acid, in plants, because it has been shown that a green 
leaf placed in darkness and in an atmosphere deprived of 
oxygen nevertheless exhales carbonic acid, the emission 
of which under such circumstances cannot of course be 
connected with any corresponding inhalation of oxygen. 
Though going on constantly, the energy of the oxi- 
dizing process is much less than that of the opposite de- 
oxidizing process, carried on when the chlorophyll cells 
are exposed to the light. Deprived of oxygen, the move- 
ments of the protoplasm, the movements of the roots 
and of the leaves cease, other manifestations of activity 
are put a stop to, and the plant dies of suffocation. 
Moreover, it has been shown that each cell consumes its 
own supply of oxygen, and if that fails it will die, even 
though adjoining cells be provided with the gas. In this 
particular then the cells act, not in concert, but indi- 
vidually (Van Tieghem). It is not essential that the 
oxygen should be in a free state ; 1t may be utilized by 
plants from a compound containing oxygen, and from 
which it may easily be obtained. An instance of this is 
afforded in the case of the disease of animals known as 
“‘charbon,” which is now known to be caused by the 
existence in thé@blood of the animal affected of a micro- 
scopic plant (Bacillus anthracis), which lives in the blood, 
and which, not finding sufficient oxygen in its serum or 
liquid portion, decomposes the matter contained in the 
red corpuscles and utilizes the oxygen they afford. To 
live itself, it deprives the creature in which it is estab- 
lished of its oxygen, and thus not only kills it by suffo- 
cation, but eventually cuts off its own supply of food. 
The effect of depriving a plant which contains glucose 
of its oxygen is to convert that glucose into alcohol. . 
Thus fermented liquors, such as beer, wine, etc., owe 
the alcohol they contain to the temporary cutting off of 
