162 College of Forestry 
plex compounds of living organisms to the simple ultimate 
products. 
By the advancing decomposition, the nitrogen which in 
organic combinations is accessible to plants with difficulty, 
is carried over into compounds easily absorbed. In propor- 
tion as the carbohydrates are attacked by destructive agen- 
cies, the residue tends to constitute itself into a complex of 
increasing resistance. This entire group of by-products is 
extremely ill-defined and requires much more exhaustive 
investigation to establish their definite relationships with the 
carbohydrates from which they result. The partially decom- 
posed material of woody plants forms a particularly vague 
and indefinite group of substances containing all the non- 
volatile products of fungal, enzymic and oxidative reactions 
on the plant residues. <A detailed study of this group thus 
being out of question, we can merely ascertain what relation 
it bears to the original woody substance,’ since we have 
already discovered, in a general way, the particular con- 
stituents of the woody plant that entered into its formation. 
The formation of the brown humic substance in woods 
decayed by Polyporus pargamenus is similar to the deserip- 
tion given by von Schrenk (1900*) of that occurring in 
pecky cypress, except that none of the intermediate stages 
of the humification described by him could be detected. In 
the decay of dicotyledonous woods by Polyporus pargamenus 
the transformation of lignified membranes to humic sub- 
stance is much greater and decidedly more abrupt than 
occurs in coniferous woods attacked by the same fungus. 
After comparing the description of the formation of the 
humic compound with that of the method of disintegration 
of the wood, it seems that the formation of humic compounds 
is due to certain chemical changes in the normal lignified 
membranes, as a result of which certain of its constituents 
which ordinarily react with phloroglucin-HCl, are extracted. 
These preliminary changes are followed by more profound 
changes ending in the formation of certain by-products of 
humic nature. These substances ordinarily diffuse through 
the adjoining cells, and ultimately harden within the lumina 
