72 OUTLINES OF FORESTRY. 



the " schullkrankheit," often affects the pine for- 

 ests. Trees attacked by this disease soon present 

 the appearance of having been burnt over, their 

 boughs and branches rapidly dying or drying up. 

 The cause of the disease is not exactly known. It 

 has, however, been ascribed to the presence of a 

 fungous growth. 



In some parts of Iowa a fungous growth on the 

 cottonwood trees has resulted in considerable dam- 

 age to them. The fungus appears as an orange- 

 yellow dust on the lower surfaces of the leaves. 



The animal enemies of the forest, like the winds, 

 running water, or the avalanche, produce their 

 most marked action on the borders or edges of the 

 forest. 



In the deep recesses of the forest the vegetable 

 kingdom holds almost undisputed sway. The life- 

 giving power of the sun's light, and, to a great 

 extent, that of its heat, are dissipated by the dense 

 foliage that almost completely shuts out the light 

 from the dank, gloomy ground. Animal life, to 

 a great extent, is crowded out. "Wherever the 

 sunlight freely enters, animal life appears in 

 myriad forms, until at length the forest again 

 chokes it out of existence. 



The animal enemies of the forest are too numer- 



