468 University of California Publications in Botany [Vol- "^ 



there may be only one or two, but in others the lumen may be almost 

 filled. In all cases the mycelium varies considerably in size, the walls 

 are thin, and branching is infrequent. The lateral tubercles are 

 present upon the walls of some of the hyphae. 



Wherever the mycelium is found in wood in earlier stages of decay 

 there is present a series of small, globular masses of a brown exudate. 

 The mycelium of Schizophyllum growing upon artificial media pro- 

 duces a like substance, so that found in the wood is probably pro- 

 duced by the hyphae. In certain regions the droplets are so numerous 

 that the wood is discolored. They account for the black or dark brown 

 layers often seen near the edge of the decayed areas. In regions of 

 advanced decay they have entirely disappeared. 



Cross-sections through the limb of a living tree which was infested 

 with the fungus in a narrow area along one side of the limb showed 

 that the infected area extended in a radial direction to the center of 

 the limb. Some pieces of this limb were placed in moist chambers. 

 In a few days tufts of hyphae grew out of the wood. at the edges of 

 the infected area near the living wood and only a few scattering threads 

 could be seen in the central part of the discolored tissues. Thin sec- 

 tions also disclose the fact that the greater part of the vegetative 

 mycelium is near the living wood in partially killed limbs or trunks 

 of trees. 



The decay is marked at first by a darkening of the tissues. There 

 are dark brown or black layers near the edge of the darkened areas. 

 At later stages delignification sets in, and the decayed areas become 

 straw-colored. The cell walls become softened, but retain their struc- 

 ture for a long period. The mycelium of Schizophyllum is frequently 

 found in areas of advanced decay along with the hyphae of other 

 fungi, and it is difficult to determine how much of the decay is due to 

 the work of Schizophyllum commune alone. 



5. GEOWTH UPON FEESH WOOD AKD LIVING TISSUES 



Freshly cut pieces of Acacia wood were placed in moist chambers 

 and spores of Schizophyllum were planted upon different tissues. 

 Acacia wood was chosen because sporophores are found in abundance 

 upon the dead wood of this tree. The pieces of wood were kept moist 

 enough to cause the spores to germinate. The experiment was carried 

 on for two months. At the end of that time it was found that the 



