10 BULLETIN 212, U. 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 deyelopment of more mature 
growth. 
From the standpoint of merchantability, wood-destroying fungi in 
the liying tree are in almost all regions a negligible quantity. The 
two most important are Trametes pini (Brot.) Fr. and Polyporus 
scJiweinitzii Fr. These, howeyer, do not produce any appreciable 
decay till after the tree reaches its period of decline, which is attained 
after a comparatiyely rapid early growth. This period may be 
placed approximately at from 60 to 80 years. 
The wood of dead jack 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 comparatiyely 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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WASHINGTON : GOVERNMENT PRINTING OFFICE ; 1915 
