DISEASES OF TAXODIUM AND LIBOCEDRUS. 61 
A number of observers still maintain that fungi or bacteria 
are active in bringing about humification. Thus Héveler * 
finds that in the humus of a forest the mycelia of fungi 
initiate the process of humification. These mycelia are 
brown in color and are found in every humus soil. They 
belong to many different fungi and are characterized by 
possessing clamp connections. Cladosporium humifaciens 
Rostrop, he regards as the form most frequently present. 
In decaying trees, and in such as are attacked by various 
fungi, such humus compounds are frequently present; they 
have been classed as decomposition products without fur- 
ther statement as to their origin. In decaying masses 
numerous fungi usually grow all through the mass, which 
makes it difficult to decide what the true humifying agent 
is. In the cypress a humus compound usually appears 
in the cells in which a definite fungus mycclium is grow- 
ing. The same is true and probably more marked where 
the mycelium of Trametes Pini grows in pine wood. The 
latter turns red-brown very soon after the mycelium has 
entered the wood, and examination shows that this color is 
due to a humus compound. No humus compound is pres- 
ent in sound wood. This behavior of the compound 
makes it seem probable that the fungus in some way changes 
the cell-walls, and that the humus compound is one of the 
direct products of this change. 
FERMENTS. 
In the decomposition of wood it has been assumed that 
ferments take an active part. Enzymes which attack cellu- 
lose and lignified membranes are known. De Bary f and 
* Hoveler, W. Uber die Verwerthung des Humus bei der Ernihrung 
der chlorophyll-fihrenden Pflanzen. (Prings., Jahrb. fiir wiss. Bot. 
24: 290. 1892.) 
¢ De Bary, A. Uber einige Sclerotinien und Sclerotienkrankheiten. 
(Bot. Zg.44:377. 1886.) 
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