62 MISSOURI BOTANICAL GARDEN. 
Marshall-Ward * isolated ferments which corroded cellulose 
membranes. Brown and Morrisf discovered a ferment 
in germinating barley grains, and Vignal ¢ 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 Tazo- 
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.) 
t+ Brown and Morris. Jour. of Chem. Soc. 57 ¢ 505. June, 1890. 
¢ Vignal. Cont. & l'étude des bactériacées. (Thése. Paris.) 
40 
