266 



Mycologia 



and have a brown color. The brown color is due to the presence 

 of small brown globules possibly of some substance from the 

 wood, toxic to the fungus and isolated in these spots. 

 Chemical tests used to detect the presence of cellulose : 



1. Iodine in KI solution followed by treatment with weak 

 sulfuric acid (1-3) colors cellulose blue; 



2. Chloriodide of zinc colors cellulose blue ; / 



3. Iodine in alcohol colors cellulose faintly yellow. 

 Of lignin : 



1. Iodine in alcohol colors lignin deep yellow; 



2. Phloroglucin followed by hydrochloric acid colors lignin 

 bright carmine red wherever present ; 



3. Carbolic acid and hydrochloric acid followed by exposure to 

 daylight for an hour color lignin green. 



The use of these tests showed the removal of the cellulose 

 from the rays in the early stages. Soon afterward, however, the 

 tracheids in the spring wood were attacked and the middle lamella 

 laid bare, so that a test at just the right stage indicated a small 

 amount of free cellulose present here. As the rot progressed, 

 tests for cellulose failed altogether, and those for lignin grew 

 fainter. However, phloroglucin and hydrochloric acid indicated 

 a small amount present in the most rotten wood. This action of 

 the fungus indicates that it secretes both lignin and cellulose dis- 

 solving enzymes during its development. 



In some respects the rot is very similar to that caused by P. 

 borealis in the same host. As that seems to have the checks in the 

 spring wood also, the presence of the before mentioned black 

 spots and lines in the case of the decay caused by P. tsugae is the 

 chief means of identification when sporophores of the fungus are 

 not present. 



The rot can usually be detected, in the older stages at least, by 

 the presence of the sporophores with their very glossy red sur- 

 face and the white context from the crust to the tubes. The rot 

 in the wood is characterized by its being primarily a sap rot 

 (though it finally rots the heart- wood also) producing a porous 

 condition, with numerous white checks in the spring-wood and 

 blacks spots scattered through the rotted area. 

 New Brunswick, N. J. 



