36 FIRST BOOK OF FORESTRY 



We see that cold affects the forest just as do a poor 

 soil and too much or too little water. It simplifies 

 the composition of the forest and, in extreme cases, 

 stunts its growth. But we also observe that this 

 effect is not very serious within the borders of our 

 land ; that our most important hardwood trees extend 

 far north and south ; and that tlie effect is less important 

 for our sandy or poorer lands than for more fertile 

 districts. 



Were we to incpiire into the growth and behavior of 

 our forest trees along the same route of travel north and 

 south, we should find the effect even more important. 

 We should learn that oak and maple in Tennessee sprout 

 well ; in the Lake Superior country, with difficulty ; that 

 most trees bear seed oftener and more abundantly, and 

 that young growth starts more easily, grows faster, and 

 stands more shade in warm districts than in cold. Here 

 and there, to be sure, there would be some exceptions to 

 this rule, but they would be just enough to emphasize its 

 general truth. 



Having learned the importance of warmth and sun- 

 shine, we realize why, in our northern states, the forest 

 on the south side of a ridge often differs so radically from 

 that on the north side. It is the warmth and light of the 

 sunny south exposure which permits a greater variety of 

 trees and banishes the frugal conifers to the colder, darker 

 north side. 



