The North American Forest 25 



them, while in other years only here and there a 

 few are ripening. Consequently it is only in seed 

 years that there is much hope for any seeds to find 

 a favorable sprouting place. But even then it may 

 happen that not one of them has such luck. The 

 condition of the ground has much to do with this. 

 It may be that by one cause or other, as, for in- 

 stance, too much moisture or too great dryness, it 

 has become unfavorable to the seedlings, either by 

 reason of its chemical or mechanical condition. The 

 older trees are little affected by the change, for 

 they send their roots deeply into the subsoil and the 

 character of the surface layer is of relatively little 

 importance to them. But the seedling depends for 

 its life upon the condition it finds in this top-soil. 

 More often the ground is shaded too much either 

 by the crowns of the old trees themselves or by the 

 undergrowth, which in turn may consist of former 

 generations of young trees of the same species or 

 of shrubs belonging to entirely different kinds of 

 plants. In still other cases the ground may have 

 been invaded by grasses or herbs, forming a matted 

 tangle of roots and stems which make it difficult for 

 the tree seeds to sprout. Under any of these and 

 similar conditions long periods may elapse during 

 which no reproduction of trees takes place, and the 

 supply of many seed years may go to waste. But 

 sooner or later an opportunity will come ; and the 

 trees are always on the lookout to take advantage 

 of accidents. One of the commonest of such acci- 

 dents is the death and fall of one of the giants of 



