12 



death. Others grow within the heartwood, in which case the tree maj'' 

 remain alive as long as the trunk is strong enough to uphold the 

 crown of l)ranches. Some of these fungi can grow both as saprophytes, 

 i. e. , on dead wood, or as facultative parasites on living trees. In the 

 following only those fungi are considered which so destroy the wood 

 of the trees as to render it unlit for lumbering purposes. 



The fungi to be described all belong to the PohjjWTei. Their sporo- 

 phores form during the summer, and in several cases grow on dur- 

 ing the winter months. They discharge their spores into the air 

 in vast numbers, and these are carried to great distances by the 

 wind. The spores germinate, under favorable conditions, in a 

 wound or on the roots, and the mycelium makes its way into the 

 inner parts of the tree, where it flourishes for a shorter or longer 

 period, when the fruiting organ is again formed. The length of time 

 which is required for the formation of the sporophores is variable, 

 and is known for very few species. In some cases the sporophores 

 grow onl}^ on the living trees; in other cases, again, they form for 

 many years on the dead stumps or fallen trunks. Seasonal variations 

 are to be met with. Some years, when it is exceptionally moist, the 

 fruiting forms grow in great numbers, while during a dry summer 

 very few are to be found. 



EXTENT OF DESTRUCTION. 



The amount of destruction which these fungi do is actually very 

 large. As has been said, the casual observer does not note a dead tree 

 here or there, but he is struck with the destruction wrought by forest 

 fires. In certain localities the older trees are likely to become infected 

 by one fungus or another, and it is a common saying of the lumberman 

 that "the older trees are always rotten." If all the dead trees in a 

 forest could be brought together, their number would truly be a sur- 

 prise to lumbermen, the majority of whom have no appreciation of 

 even the approximate destruction which is wrought in the forests in 

 this way. Without extended cruisings it would be hazardous to make 

 any more definite statement for the present than this: The number of 

 dead and decayed trees is sufiiciently large to represent a considerable 

 loss in capital, and warrants making efiorts to prevent the destruction 

 of what would be valuable timber if harvested in time. 



EXTERNAL EVIDENCES OF DECAY. 



It is often a matter of considerable importance to recognize which 

 trees in a forest have been attacked by fungi, so that these trees may 

 be removed before the}^ are completely destroj^ed and before there is 

 any opportunity for the formation of sporophores. Trees which are 

 in an advanced state of decay can usually be recognized by the fact 

 that they have the fruiting organ of one or another fungus growing 



