FOREST PATHOLOGY. IN FOREST REGULATION. 13 



on the members of this group must be left to the future. At the 

 present time we are more interested in the preservation of our actual 

 timber, including such values as will be formed in the near future. 



Actual timber values are seriously endangered by wood-destroying 

 fungi, all of which belong to the Hymenomycetes. With the exception 

 of a very few (Armillaria mellea, Fomes annosus), which in attacking 

 living roots first cut down the increment of their host and then invade 

 the wood of the bole, they all inhabit the heartwood and generally 

 leave the sapwood intact. As the principal timber values are stored 

 in the heartwood, the enormous damage they are able to cause is all 

 the more in evidence. All of these fungi are adapted to given hosts 

 or groups of hosts; these groups are seldom very large. Polyporus 

 amarus, for example, the cause of the extremely destructive heart 

 rot of Libocedrus decurrens, can not grow, as far as is known, in any 

 other host species. Trametes pini, on the other hand, attacks a 

 number of pines, Douglas fir, and other conifers. The composition of 

 the stand, as well as the representation of species, is therefore an im- 

 portant factor in the ecology of these fungi. Only those fungous 

 spores which land on trees of the species to which they are adapted 

 have a chance after germination to enter into the tree. 



Being strictly heartwood inhabiting, these fungi, with the excep- 

 tions mentioned above, can, of course, only attack trees which already 

 have formed heartwood. But as they are unable to penetrate the 

 bark, they are harmless unless their spores are carried on to some 

 wound or opening (branch stubs) in the protective skin represented 

 by the bark. The longer the host is exposed to wounding, the greater 

 will be the chances for infection. 



As might be expected, therefore, the losses from decay in standing 

 living trees are enormous in virgin forests. Even in the best managed 

 forests of Germany losses from decay are heavy. Moller, 1 in figuring 

 the damage done by Trametes pini in the pine forests of the Prussian 

 Government, arrives at the astounding figure of more than 1 million 

 marks (about $250,000) annual loss from this source alone. In the 

 period from 1905 to 1908 the Prussian Government spent $87,480 in 

 the control of Trametes pini in its pine forests. 2 In 1914 this sum had 

 increased to about $120,000. 3 



In American literature no reliable figures are available relating to 

 the annual loss from decay in standing timber in virgin forests. 

 Such figures can be obtained only by exact studies on representative 

 areas, the methods of which the writer has been trying to work out 



1 Moller, A. Uber die Notwendigkeit und Moglichkeit wirksaruer Bekampfung des Kiefernbaum- 

 schwammes Trametes pini (Thore) Fries. In Ztschr. Forst- u. Jagdw., Jahrg. 36, 1904, Heft 11, pp. 677- 

 715, pis. 4-5. 



2 Moller, A. Der Kampf gegen den Kiefernbaumschwamm. In Ztschr. Forst- u. Jagdw., Jahrg. 42, 

 1910, Heft 3, p. 133. 



3 Moller, A. Der Kampf gegen den Kiefera- und Fichtenbaumschwamm. In Ztschr. Forst- u. Jagdw., 

 Jahrg. 46, 1914, Heft 4, pp. 193-208. 



