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 f figures a fungus, Pero- 

 nosporites antiquarius from a stem of Lepidodendron (the 

 same is also found in coal beds). Conwentz J found a 

 mycelium in fossil wood of Rhizocupressinoxylon unira- 



* Unger, F. Chloris protogaea. 1847. 



t Williamson, W. C. On the organization of fossil plants of the 

 coal measures. Calamites. (Phil. Trans. K. S. L. 161 : 477. 1871.) 



$ Conwentz, H. Fossile Holzer von Karlsdorf am Zobten 27. 

 Danzig. 1880. 

 42 



