DISEASES OF TAXODITJM AND LIBOCEDRUS. 



A number of observers still maintain that fungi or bacteria 

 are active in bringing about humification. Thus Hoveler * 

 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 

 Eo strop, 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 mycelium 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. Tiber die Verwerthung des Humus bei der Eraahrung 

 der chlorophyll-fiihrenden Pflanzen. (Prings., Jahrb. fur wiss. Bot. 

 24 : 290. 1892.) 



t De Bary, A. Uber einige Sclerotinien und Sclerotienkrankheiten. 

 (Bot. Zg. 44:377. 1886.) 



39 



VERSI1" 



