10 



large holes the amount of wood fiber which has been reduced to cel- 

 lulose is very considerable (often as much as 300 grams of this 

 cellulose is present). The masses of cellulose consist of individual 

 wood cells, which can be pulled out with a needle. The whole mass 

 is very soft and can be squeezed between the fingers much like the 

 wood pulp in a paper mill after treatment with zinc chloride. In 

 older holes the white lining is almost absent (see largest hole, PI. Ill), 

 the walls being covered with a felt of soft brown mycelium, which 

 often assumes very fantastic shapes. This is especially true where 

 the proximal end of a branch projects into a hole, the wood of the 

 trunk surrounding the branch having been destroyed and the more 

 resinous end piece of the branch resisting the attacks of the fungus. 

 Around this end piece the mycelium forms spherical masses of the 

 size of a small marble. These felts are dry and elastic, and sometimes 

 there are 20 or 30 of them together. 



The holes are generally in the center of the trunk and extend lon- 

 gitudinally through it, one above the other, with partitions of sound 

 wood between. (Fig. 1.) In the larger trees there are frequently 

 several holes in the same cross section. (PI. III.) 



These holes may ultimately join here and there by the absorption of 

 the intervening walls. They are largest at the base of the trunk, the 

 size diminishing from the base upward, as shown in tig. 1. The 

 distance between the holes varies from 6 inches to 3 feet. 



CHANGES WHICH THE FUNGUS CAUSES IX THE WOOD. 



The chanofes which occur in the wood after the entrance of the 

 mycelium are of two kinds. In the first kind the original red color 

 fades somewhat, the change being barely noticeable when the light is 

 reflected at an angle. Very soon, however, the wood fibers in a given 

 region turn white, showing that the lignin is being destroyed. Such 

 a staoe is shown in PI. I. In this case the wood fibers of about eight 

 annual rings are affected, the change being almost uniform through- 

 out the whole mass. With the increased growth of the mycelium the 

 wood fibers of the adjoining annual rings are attacked and are changed 

 to cellulose. At a later stage the central mass is entirely absorbed 

 and leaves a small hole, which gradually increases in size until it 

 becomes 6 to 8 inches long and 2 to 3 inches wide. (PI. II.) Around 

 this cavity wood fibers in various stages of decomposition occur, 

 some just beginning to change and others entirely reduced to cellulose. 



In the second form of decay the red color disappears very slowly 

 and the wood fibers gradually become brittle and finally fall apart in 

 tangential layers. In PL II a wide ribbon of such wood fibers is shown 

 extending from the left of the white area downward. The cavity is 

 partially filled with wood fibers such as these, together with the 

 mvcelium. The cellulose fibers are never found loose in the cavity, 



