MISSOURI BOTANICAL GARDEN. 



Marshall-Ward * isolated ferments which corroded cellulose 

 membranes. Brown and Morris t discovered a ferment 

 in germinating barley grains, and Vignal J records a case 

 of a ferment secreted by Bacillus mesentericus, disso- 

 ciating vegetable cells by destroying the middle lamella. 

 The action of the wood-destroying fungi is such, that 

 Hartig and others have attributed the decay which 

 they bring about to some enzyme excreted by the 

 hyphae. That the same fungus produces several such 

 enzymes must follow from the different effects which the 

 same fungus has on the same wood. If then we assume 

 such a cytohydrolytic enzyme to be formed by the Taxo- 

 dium fungus, we find it destroying the wood about a certain 

 center. As the mycelium grows along the vessels more 

 readily than across them, a long hole is formed. As 

 a result of the action of the fungus on the cell-walls, an 

 acid humus compound is formed, which is deposited in the 

 cells surrounding the center of fungus activity. It is not 

 far to make the further assumption that after a time the 

 amount of humus compound would be sufficiently great to 

 stop the further development of the fungus in that area. 

 The hyphae however pass through this area to a new center, 

 where they begin over again. This would explain why the 

 holes are approximately of the same size. The amount of 

 antiseptic substance necessary to prevent further decompo- 

 sition would be about the same in each area, and it would 

 require the decomposition of a definite amount of wood to 

 form this quantity. It may be objected that the holes are 

 not always bounded by solid wood, but often run together. 

 This would be explained by supposing the amount of 

 humus formed at that point not sufficient to overcome the 

 influence of the enzyme. 



The conditions under which enzymes are active are 



* Marshall- Ward, H. On a lily disease. (Ann. Bot. 2 : 346. 1888.) 

 f Brown and Morris. Jour, of Chem. Soc. 57 : 505. June, 1890. 

 } Vignal. Cont. a 1'gtude des bactriac6es. (These. Paris.) 

 40 



