EXOGENOUS SERIES NEEDLELEAF WOODS. 



'55 



The insect and fungus enemies of spruce trees cause great 

 losses, and have received much attention.* Dead and fallen 

 trunks are sometimes so numerous as to obstruct passage 

 through the forest. t The largest and best trees seem most 

 liable to attack. Dr. Hopkins states that the " spruce- destroying 

 beetle" (Dendroctonus piceaperia] is accountable for much of 

 this damage as accomplished in the East. These beetles gain 

 entrance through crevices in the bark and cut grooves upon the 

 sensitive outer sapwood. The resins that collect in the freshly 

 cut tunnels are ejected by the beetle, and form what are known 

 as "pitch tubes." These, together with the wood particles, 

 serve to mark trees that have been recently attacked. There is 

 an intimate connection between the attacks of insects and those 

 of fungi. Fungi may lodge in and infect wounds that have been 

 caused by insects. Von Schrenk associates many species of 

 fungi with living and dead spruce trees. Much wood remains 

 sound for some time after the physical death of the tree, and 

 is clearly available for lumber and paper pulp. 



The following table sets forth the primary distinctions be- 

 tween the spruces and the pines, firs, and hemlocks: 



* " Insect Enemies of Spruce in the Northeast" and " Insect Enemies of the 

 Forests of the Northwest." Hopkins, U. S. Div. Entomology, Bulletin 28 and 21; 

 also " Diseases New England Conifers," von Schrenk, U. S. Div. Vegetable 

 Physiology and Pathology, Bulletin No. 25. 



t '-'Windfalls" may result from insects, fungi, age, or tornadoes. Trees are 

 piled upon one another like jackstraws. Trunks and limbs intermingle and are 

 sometimes penetrated by wiry, second-growth saplings. Passage through such a 

 district is made by cautiously walking back and forth, up and down, over trunks 

 and limbs. It is sometimes impossible to proceed more than two or three miles 

 daily in a straight line. The writer was within sound of the creation of one 

 windfall by tornado. Snow, " Transactions Am. Inst. Mining Engineers, 1899," 

 also Pa. Dept. Agriculture, Third Annual Report. The term "Blow-down" is 

 sometimes used. 



