64 MISSOURI BOTANICAL GARDEN. 
out, this method of separating enzymes is very unsatisfac- 
tory, as it weakens the enzyme and may even destroy it. In 
this case it is probable that much of the precipitate consisted 
of soluble humus compounds, and as these are likewise 
precipitated by alcohol a separation becomes difficult. 
As the humus compound is insoluble in water (except a 
minute trace) it is difficult to add it to any culture media. 
It was dissolved in very weak KOH and added to agar and 
bouillon tubes which were inoculated with various bacteria 
and fungi. To a similar series of agar and bouillon tubes 
the KOH solution was added and likewise inoculated. In 
this double series no additional inhibitory effects due to the 
humus compound were evident. 
The conclusions arrived at in this chapter indicate that 
the humus compound found in the wood surrounding the 
holes is formed because of the action of a fungus on the 
cell-walls of the wood, and that it is probably one of the 
products effective in preventing the unlimited spread and 
destructive action of the disintegrating powers of that 
fungus. 
AGE OF THE FUNGUS. 
Taxodium distichum is an interesting tree in that it is one 
of the surviving members of a race of trees which were 
prominent in geologic times. Any disease which it is 
affected with may possibly have come down to the 
present day with its host. But few fungi are known in 
fossil condition. Unger * describes mycelia from the wood 
of a Tertiary tree; Williamson ¢ figures a fungus, Pero- 
nosporites antiquarius from a stem of Lepidodendron (the 
same is. also found in coal beds). Conwentz t found a 
mycelium in fossil wood of Rhizocupressinoxylon unira- 
* Unger, F. Chloris protogaea. 1847. 
+ Williamson, W. C. On the organization of fossil plants of the 
coal measures. —Calamites. (Phil. Trans. R. S. L. 1612477. 1871.) 
t Conwentz, H. Fossile Hélzer von Karisdorf am Zobten 27. 
Danzig. 1880, 
42 
