518 Our Surroundings 



the green leaves, thus destroying their means of making food, or 

 by sucking the sap through the leaves and bark, which takes away 

 food already made. Decaying branches, dead trees, and stumps 

 are often the breeding places of insects that later may attack liv- 

 ing trees. Among the insects most harmful to trees are the elm 

 leaf beetle, the tussock moth, the gypsy moth and the brown tail 

 moth. 



Fungi. Trees, like all other living things, are subject to dis- 

 eases, the most common of which are caused by fungi. Fungi 

 are low forms of plant life unable to make food, since they possess 

 no green parts. They develop from spores which are so very light 

 and small that they are easily carried by the movement of the 

 air from tree to tree. Falling on a growing part where the surface 

 has been broken, they germinate, and their thread-like structures 

 grow into the substance of the tree, feed on its tissues, and soon 

 exhaust its vitality. One of the most harmful fungi is the white 

 pine blister rust, which has caused the destruction of millions of 

 dollars worth of white pine trees. Other fungi harmful to trees 

 are the common white and yellow wood-rots. 



Forestry. The object of forestry is the preservation and 

 cultivation of existing forests, and the restoration of forests that 

 have been destroyed. Forestry is now regarded as a vocation and 

 many men well trained in this line are rendering excellent service 

 to their country. Through their work they help to insure a con- 

 stant supply of lumber for the country's needs, and a more regu- 

 lar flow of water in streams and rivers. Their reforesting also 

 protects the land against destructive erosion and is invaluable in 

 the preservation of our native wild life. 



The value of forestry has been recognized for centuries by 

 some of the leading countries of Europe. Germany and Switzer- 

 land were the .first nations to try to preserve their forests by in- 

 sisting on judicious cutting and on reforestation. No nation can 

 afford to destroy its forests ; on the contrary, it should try in every 

 way to conserve them. 



Our own country was somewhat slow in recognizing the neces- 

 sity of caring for her forests. Not until 1875 did the United 

 States take any real interest in their preservation. However, when 



