THE CONIFEROUS FORESTS 239 



On the other hand, the Lichen {Usnea harbata) 

 (Plate XLIV., Fig. 2), known as the Old IMan's 

 Beard Lichen, so frequently seen depending from the 

 boughs, especially the dead branches of the Spruce 

 or Larch, to which it is attached, is not, despite 

 statements to the contrary, known to be directly 

 harmful to the tree. 



It has been well said that ** the Pine forests play a 

 most important part in the natural economy of the 

 Alps, and their preservation is a matter of viUil 

 consequence to the future inhabitants." What follows 

 when a country has been deprived of its forests is well 

 seen in certain districts in India and Ceylon. The 

 nature of the climate has been changed, and has 

 become drier and hotter than formerly. A forested 

 country tends to produce a more humid atmosphere 

 than a treeless district, and, in Switzerland, the 

 atmosphere is probably drier to-day than it was a 

 hundred years ago. Again, to a greater degree than 

 is usually realised, the forests afford the only efficient 

 safeguard which prevents the valleys and lower 

 pastm^es being overwhelmed with avalanches in 

 winter and floods in summer. Often the former fail 

 to melt completely for several summers after their 

 fall, and the ruin of the Alpine meadows and pastm'es 

 is rendered still more complete by the confusion of 

 rocky debris which they bring down in their train. 



We will now discuss the trees forming the Alpine 

 forests. 



