60 AGRICULTURAL BACTERIOLOGY 



encc to the causal forms or to the chemical processes in- 

 volved. In the decomposition of certain carbohydrates the 

 process is more simple and may be followed in its essential 

 details. Starch may be acted on by certain organisms 

 through their enzymes, and a complex sugar formed, as 

 maltose (C^IT^O^). The latter, by the same organism or 

 by another, may be changed to a simpler sugar, glucose 

 (C H 12 O fl ), which may be fermented by yeasts with the for- 

 mation of carbon-dioxide and alcohol (C 2 II 5 OH). The 

 former compound is available for the green plant. The 

 latter may be used by certain bacteria which oxidize it to 

 acetic acid (C 2 H 4 2 ), which, in its turn, is changed by 

 molds to carbon-dioxide and water. The elements con- 

 tained in the sugar are now all available to the green plant. 

 It is not to be understood that this is the particular path 

 always followed in the decomposition of starch. Innumer- 

 able deviations, both as to organisms and products, may 

 occur. It is presented simply as an example of metabiosis. 

 The initial steps in the process described can be carried 

 out under anaerobic conditions. The decomposition of acids 

 is a process for which the molds are especially fitted. These 

 are all aerobic. Therefore, if the process is to go on to com- 

 pletion, aerobic conditions must be established. It may be 

 stated as a general fact that the initial processes in all de- 

 composition may take place under anaerobic conditions, but 

 that the final steps can go on only under aerobic conditions. 

 This fact, which is of great importance in many practical 

 relations, finds its explanation in that the initial steps are 

 accomplished largely by the addition of water to the mole- 

 cules to be broken up. This process is termed hydrolysis. 

 A simple splitting up of the molecule may also occur. The 

 final stages involve the addition of oxygen to the molecule. 

 All of these processes are illustrated in the equations pre- 

 sented : 



