14 BULLETIN 871, U. S. DEPARTMENT OF AGRICULTURE. 



STRUCTURE OP THE DISEASED WOOD. 



The structure of the decayed wood in mature pockets was found 

 to be practically as described by Von Schrenk (26, p. 70-71). In the 

 very early stages of decay (immature pockets), cracks in the cell walls 

 such as he describes for old pockets, which were most common in the 

 pits, were rather rare. It was also found that cracks often started 

 from the holes in the cell walls made by the hyphse of the fungus. 

 The color of the decayed wood varies from light to dark brown, de- 

 pending on the state of decay. 



In some of the decayed wood examined the bordered pits gave 

 much the same appearance as is often presented by starch grains in 

 a plant cell which have been partially corroded by diastase. Further 

 examinations showed this condition of the bordered pits to exist in 

 badly decayed wood, in slightly decayed wood, in the straw-colored 

 wood between the pockets, and in sound wood. Immediately upon 

 treatment with xylol, and more slowly with oil of turpentine, the pits 

 resumed their normal smooth appearance; consequently, the con- 

 dition is the result of a deposit on the membrane of the pits, but as to 

 the nature of the substance deposited or the cause of its deposition 

 the writer is unable to give any information. At least, the fact that 

 the deposit was found on the pits in sound wood proves that it is in 

 no way a result of the action of the fungus. 



Badly decayed wood, slightly decayed wood, straw-colored and 

 brownish colored wood between the pockets, and sound wood were 

 treated with various reagents, the results in each case being practi- 

 cally identical. Anilin sulphate colored the cell walls a brilliant 

 yellow. A cherry to violet-red stain was produced by treatment 

 with phloroglucin and hydrochloric acid. Chloriodid of zinc and 

 alcoholic iodin with sulphuric acid both stained the walls a yellowish 

 brown color. After treatment for 12 hours with Javelle water, the 

 wood turned a yellowish brown upon the application of chloriodid of 

 zinc, and a brilliant yellow with the addition of anilin sulphate. 

 The above tests demonstrate that the lignin compounds in the cell 

 walls are not changed, in so far as our present knowledge of the nature 

 of so-called lignin enables us to judge. Therefore, it seems probable 

 that the fungus extracts from the cell walls either the cellulose or 

 some other compound yet unknown. 



THE MYCELIUM. 



Hyphae were very rare in the pockets of badly decayed wood or in 

 the apparently sound wood immediately surrounding these. Proof of 

 their having been quite commonly present, however, was afforded 

 by the tiny holes in the cell walls of the decayed wood through which 

 the hyphae had passed. In the slightly decayed wood and the wood 





