The North American Forest 17 



ridge. The conditions there would be below their 

 moisture minimum ; while a black spruce, for in- 

 stance, will grow in a Northern Wisconsin swamp 

 no less than on a dry rock in the Adirondacks, be- 

 cause it is adapted to a very large range of moisture 

 conditions. 



As to light, dendrologists have divided trees into 

 two classes, light-loving and shade-enduring species. 

 The two classes, however, connect by imperceptible 

 transitions. Generally speaking, the needs of a tree 

 as regards light can be told by the character of the 

 shade its own crown makes. The oaks, for instance, 

 need much light, and an oak sapling that stands in a 

 dark, shady place will never grow to be a good-sized, 

 healthy tree. Now, everybody must be struck with 

 the light character of an oak grove, where the sun 

 rays everywhere penetrate to the ground and 

 paint fantastic figures on the vigorous growth of 

 grass and herbage. A maple grove is much darker, 

 and if you enter a wood composed of beeches or 

 hemlock, you find yourself in almost nocturnal twi- 

 light, where no ray of the sun succeeds in reaching 

 the ground. The need of light for the light-loving 

 trees is particularly great in their youth ; while on 

 the other hand, the seedlings of the shade-enduring 

 trees often die when they are exposed to too bright 

 sunshine. If the seed of a light-loving tree should 

 fall under the crowns of a group of beeches, it 

 would have very little prospect of growth, while 

 the young beeches would grow lustily. Here is 

 one of the ways in which species of trees carry on 



