35 



VI). A trunk like that from which the log shown in PI. VI. fig. 2, 

 was taken decays no further, and ma}" stand in the forest for man}^ 

 years. After a tree has once fallen the destruction seems to stop. 

 Two trees under observation for more than a N^ear did not change at 

 all. In both the decomposition had reached, in 1898, the stage shown 

 in fig. 2, PL VI, and in September, 1899, no further change could be 

 detected. Further observations in this connection are desirable. 

 This point is perhaps not as important from the standpoint of the for- 

 ester as the power of the fungus to form fruiting organs after the fall 

 of a tree, and this assuredly takes place with this fungus for several 

 years, as will be mentioned. 



DESTRUCTION OF FIR WOOD. 



The destruction of the wood of Balsam Fir, Ahies hahaniea^ does 

 not differ materially from that of the Spruce. White spots appear in 

 newly attacked wood, which soon grow into larger ones; the black 

 lines surround the individual holes sooner or later and then the decay 

 ceases. On PI. VII a radial view is shown of a log taken from a Fir 

 which had been blown down during the past summer. 



DESTRUCTION OF TAMARACK WOOD. 



The process of destruction is very different in the Tamarack. This 

 is proba))ly due to the different nature of the wood of this tree, which 

 seems to be far less resistant than the others. In the Tamarack the decay 

 goes much beyond that described for the Spruce and Fir. In the 

 early stages (PI. VIII, fig. 1) small white spots appear, which usually 

 occupy the entire width of an annual ring. Two or more of these 

 spots soon join, at first in a longitudinal direction, then laterally also. 

 In that way it happens that very early in the process of destruction 

 long stretches of one or more rings of wood are transformed to cellu- 

 lose. This is well shown in fig. 1 of PI. VIII. This brings about the 

 separation of one or more rings from the adjoining ones, forming in 

 that way a series of tangential plates which can readily be separated. 

 In the figure each one of the plates visible at the upper end represents 

 one amuial ring. The line of separation between the rings is always 

 at the point where the summer wood stops and the spring wood of the 

 following year })egins. As the decay continues, more and more of the 

 sound wood fibers are attacked, leaving loose cellulose fibers. When 

 most of the wood has disappeared, black lines similar to those 

 described for the Spruce appear, but as there are no such centers of 

 decay as in that tree the lines are scattered irregularly. It would 

 seem as if there were few decomposition products formed in the Tam- 

 arack, and then only at a very late date. Ultimately the tangential 

 plates become extremely thin; they are then c<)nii)osed of the more 

 resistant sunnner wood cells of this or that wood ring, which ar(> more 

 or less infiltrated with resin. The whole body of the former wood is 



