324 ANNUAL REPORT OF THE Ofif. Doc. 



uding from the filaments of the fungus, and in this exuding fluid was 

 found a ferment in concentrated form, possessing the power when 

 coming in contact with cell walls of softening and dissolving them. 

 It was also observed that the ferment acted differently on different 

 portions of the cell wall, and that its action was first upon the mid- 

 dle portion, or what is technically known as the middle lamella. This 

 was followed by a swelling of the remainder of the wall, and by the 

 appearance of distinct stratifications, which dissolve one by one in 

 turn. In the swelling of the cell walls the latter assume a semi- 

 mucilaginous consistency which has the effect of softening the entire 

 tissue. Thus plants attacked by cytase secreting fungi, such as the 

 ones named, undergo a species of soft rot. 



In addition to the preceding observations Kean and Arthur^ have 

 recently shown that the fungus JRkizopus nigricans also secretes a 

 cellulose dissolving enzyme. This latter fungus is a common cause 

 of a soft rot of the sweet potato, a result in accord with the proper- 

 ties of the fungus. It is, furthermore, probable that a large variety 

 of fungi associated with the soft rots of fleshy fruits and roots, pos- 

 sess the same property of secreting cellulose enzymes. 



A number of the higher toad-stools and shelf-fungi, are associated 

 with dry rot of timber, in which process the hard wood becomes 

 converted into a brown pulverent mass. This disintegration is af- 

 fected, it is now believed, through the ability of these several fungi 

 to produce enzymes capable of softening and in a measure at least of 

 dissolving cellulose or woody tissue. 



Besides the fungi proper, certain bacteria have been shown to pos- 

 sess the ability to ferment cellulose. Thus as early as 1850, Mitsch- 

 erlich^^ made the observation that cellulose could become soluble by 

 fermentation. In the fermentation of the potato for instance he 

 found the cell walls dissolved, and associated with this change he 

 noted the presence of a species of Bacterium. In 1875, Popff^ 

 noted the relation between the degree of fermentation of cellulose 

 and the development of certain gases, as carbon ddoxide (COo) and 

 marsh gas (CHJ. Later, in 1879, Van Tieghera showed by experi- 

 ment that a solution of cellulose was effected through the action 

 cf a micro-organism related to Bacillus amylohacter. During the 

 change, hydrogen gas was generated, also an acid, whose presence 

 gradually hindered the fermentation process. Van Tieghem's ob- 

 servations that the fermentation of cellulose was due to the latter 

 B. amylohacter was confirmed by Hoppe-Seyler^ in 1886. 



This fermentation as originally shown by Popff, and later by 

 Pioppe-Seyler and Schlosing, was accompanied by the vigorous evo- 

 lution of carbon dioxide and marsh gas, and took place in the ab- 

 sence of air. 



