10 BULLETIN 212, TJ. S. DEPARTMENT OF AGRICULTURE. 



forest problem. The fungus attacks all age classes, causing the 

 death or early suppression of trees of tender years and seriously 

 interfering with the propagation and development of more mature 

 growth. 



From the standpoint of merchantability, wood-destroying fungi in 

 the living tree are in almost ail regions a negligible quantity. The 

 two most important are Trametes pini (Brot.) Fr. and Polyporus 

 schweinitzii Fr. These, however, do not produce any appreciable 

 decay till after the tree reaches its period of decline, which is attained 

 after a comparatively rapid early growth. This period may be 

 placed approximately at from 60 to 80 years. 



The wood of dead j ack pine rapidly deteriorates under the influence 

 of a number of saprophytic fungi and may not be expected to remain 

 sound in the forest for more than two or three years. 



Jack pine is sensitive to heat, but suffers only occasionally from 

 winter injury. 



Because jack pine in general is comparatively free from a number 

 of the diseases which are common on other conifers and is resistant 

 to drought, winter injury, and frost, it is admirably suited for refor- 

 esting many of the dry sandy regions of the North-Central States. 



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