THE FOREST ORGANISM. 



223 



Fig-. 68. Winged Seeds. 1, Bass wood; 



2, Box-elder; 3, Elm; 4, Fir; 5,6,7,8, 



Pines. U. S. Forest Service. 



It is such facts as these that 

 help to account for some of the 

 facts of forest composition, 

 why in one place at one time 

 there is a growth of aspens, at 

 another time pines, at still an- 

 other oaks; and why beeches 

 spring up one year and not an- 

 other. That red cedars grow 

 in avenues along fences, is ex- 

 plained by the fact that the 

 seeds are dropped there by 

 birds, Fig. 69. 



The fact that conifers, as 

 the longleaf pine, Fig. 46, p. 

 200, and spruce, Fig. 55, p. 212, 



are more apt to grow in pure stands than broad-leaved trees, is largely 

 accounted for by their winged seeds; whereas the broad-leaved trees 

 grow mostly in mixed stands because their heavy seeds are not plenti- 



tifully and widely scattered. This 

 is a rule not without exceptions, 

 for beech sometimes covers a 

 whole mountain side, as Slide 

 Mountain in the Catskills, and 

 aspens come in over a wide 

 area after a fire; but later 

 other trees creep in until at 

 length it becomes a mixed 

 forest. 



The essential facts of the 

 relation of trees to each other 

 in the forest has been clearly 

 stated by Gifford Pinchot 

 thus :* 



The history of the life of 

 a forest is a story of the help 

 and harm which trees receive 

 from one another. On one side 

 every tree is engaged in a re- 



Fig-. 69. Red Cedar Avenue. Seeds dropped 



by birds which perched on the fences. 



Indiana. U. S. Forest Service. 



1 Gifford Pinchot, Primer of Forestry, p. 44. 



