32 PLANT LIFE ON THE FAEM. 



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 ; it 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 the 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 



