430 The Physiology of Plants BOOK in 



about this decomposition independently of the living 

 substance. This appears the more likely since Effront 

 showed, in 1898, that zymase is produced in fruits and other 

 parts of plants when they are deprived of oxygen. It may 

 be that the decomposition of the sugar is brought about 

 by the direct action of the protoplasm in such cases as 

 do not show the secretion of zymase, and that there- 

 fore the decompositions of anaerobic respiration or dis- 

 similation are not so profound as those which they replace. 

 When sugar is not present, it may be that the fermentative 

 changes affect the carbohydrate groups in the protoplasm 

 itself. At the end of the century these views remained still 

 the subjects of discussion. 



The discovery of the so-called anaerobic organisms, which 

 cannot live in the presence of oxygen, was made by Pasteur 

 in 1861. These, which are met with among the bacteria, 

 were investigated subsequently by Beijerinck 1894, Chu- 

 diakow 1896, and again by Beijerinck in 1899. Little is 

 known about their metabolism except that their energy is 

 derived from chemical decompositions. 



Pasteur's view that the purpose of intra-molecular 

 respiration is to obtain oxygen from sugar in order to 

 liberate energy by subsequent oxidation, was replaced at 

 the end of the century by the theory that this object is 

 secured by the liberation of energy during the general 

 fermentative decompositions. 



