FIG-. 20. This virgin forest, dominated by hemlock and beech, is the climax 

 of soil and vegetative evolution for this Pennsylvania area. The cycles of 

 water, soil, and air elements are meshed with the various life cycles of both 

 plants and animals. All these cycles are driven by sun power. There is an 

 annual surplus production which man can draw off without damaging the valu- 

 able climax conditions. 



PI9-. 21. Victim of chest- 

 nut blight. The fungus, 

 which has killed ntarly 

 all American chestnut 

 trees, attacks the cam- 

 bium, the living tissues 

 under the bark. The fun- 

 gus reaches a high pop- 

 ulation in the tree, ends 

 by completely destroying 1 

 its own food supply; it 

 dies along with the tree. 

 The million farmers who 

 have fled from farms 

 which they destroyed 

 should appreciate the 

 plight of this fungus. 



