90 College of Forestry 
of Polyporus pargamenus have penetrated the lignified mem- 
branes of their host in all directions they continue to exert 
on the cell-walls a solvent action which extends over a con- 
siderable area. In this way the original holes dissolved 
through the cell-wall continue to enlarge. When the enzyme 
excretions have accumulated to a sufficient amount the dis- 
solution of the cell-walls becomes wide-spread and entire 
lamelleze disappear in a definite sequence. 
The dissolution of the cell-walls is to be attributed to the 
fact that they, as a potential source of food, are valueless to 
the fungus until broken down and reduced to a condition 
suitable for translocation and assimilation. The transfer of 
the food materials through unbroken cell-walls to the various 
points of consumption can be accomplished only when they 
are in solution. In other words, they must first be converted 
into soluble substances capable of osmosis in order to be 
utilized by the fungal hyphe. The agents instrumental in 
bringing about these changes belong to those substances 
termed ferments or enzymes — substances which possess the 
power of decomposing or transforming certain organic ¢om- 
pounds into other substances w ithout themselves being 
changed or consumed in the process, By virtue of this prop- 
erty they are enabled to transform unlimited quantities of 
certain substances if the resulting product be continuously 
removed, as would be done by the fungal hyphz developing 
and ramifying through the woody substance. The peculiar 
manner in which enzymes act 1s illustrated by the following 
examples. 
In the diastatic transformation and dissolution of starch 
the starch grain is not dissolved from the surface inwards 
as a homogeneous crystal, but becomes corroded by narrow 
canals until finally it is completely disorganized and dis- 
integrated. The reduction of woody tissues by fungal hyphee 
offers another example. Wood is generally considered to be 
made up of a complex lignoc ellulose, comprising such higher 
carbohydrates as lignin, cellulose, hemicellulose, and pectic 
bodies. Each of these respective carbohydrates may be split 
into simpler constituents by being acted upon by the accom- 
