THE EARTH'S BOUNTY 



through which the sun can easily penetrate, 

 under the heading of intolerant. But there 

 are several exceptions to this general rule. 

 If the dense crown species predominate in 

 mixed woodlands, the coming generation will 

 almost surely be of the tolerant class; for 

 the seedlings of this class will steadily de- 

 velop to the sapling age, and even if retarded 

 from further growth by want of space, will 

 sustain no vital injury, but simply remain sta- 

 tionary until age or the woodsman's axe clears 

 the way for them, when they will shoot up 

 vigorously. 



But seedlings of the intolerant class 

 would pine and gradually die, or at least 

 become so debilitated that they could not avail 

 themselves of favorable conditions when they 

 occurred. As an example: If seedlings of cot- 

 tonwood, black walnut, white pine and hemlock 

 are all growing in close proximity, the quick 

 growth of the first two species would make so 

 much shade that the pine would be killed, the 

 hemlock checked, but not injured. Later a 



304 



