DISEASES OF TAXODIUM AND LIBOCEDRUS. 59 
first developed profusely, evidently stops growing. The 
threads become coated with a brown substance, which also 
fills many of the cells around the area where active decom- 
position has taken place, and saturates the cell walls. 
This humus substance is one of a class known to possess 
antiseptic properties. These facts suggest that the humus 
compound described above may in part be the agent which 
limits the disintegrating effects of the fungus. 
ORIGIN OF THE Humus COMPOUND. 
The origin of the humus compounds is still a matter of 
some uncertainty, owing to the intrinsic difficulties. Frih, 
who probably has paid more attention to this problem than 
any other investigator, says that we know as little about the 
successive stages which a plant member passes through, 
until peat is formed, as we do of the processes which bring 
about these changes.* The process is essentially a process 
of decay. Itis at present recognized that decay may be 
due to chemical processes as such, distinguished from those 
brought about through the agency of living things. 
Where decay, or more properly a splitting up of highly 
complex organic compounds into simpler compounds such 
as carbon dioxide, ammonia and water, takes place without 
the aid of bacteria or fungi, it is largely a process of oxida- 
tion. If access of oxygen is prevented no decay takes 
place. Hartig,t speaks of the decomposition of plant 
members following death due to frost, as a process due to 
the action of oxygen on the dead organic substance; fungus 
mycelia get into the tissues after a time and hasten this de- 
composition. Friht distinguishes two forms of decomposi- 
tion not due to chemical changes per se (such as oxidation) ; 
these he calls ‘«‘Gihrung’’ and ‘* Fermententwicklung.”’ 
* Fruh, J. J. Uber Torf u. Dopplerit 38. 
+ Hartig, R. Zersetzungserscheinungen, etc. 65. 
SoRTU DI. evls.Cs-Bae 
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