THE WAY OF THE WILD 53 



always on, and its complications are so many and so intricate 

 and its consequences so profound that a little space is well de- 

 voted to its analysis. 



Selective effect of natural conditions. There is a blind but 

 wholesale struggle of living things against what may be called 

 natural conditions, which assert their influence independent of 

 struggle against competition with other living beings, and gen- 

 erally before it begins. 



First of all are climatic and seasonal influences. Hosts of 

 young things, both plant and animal, come into existence only 

 to perish on the spot from adverse climatic influences. Many 

 species exist, in northern latitudes for example, only by the 

 narrowest margin, and one exceptionally hard winter will close 

 them out by the millions. In this way whole fields of wheat 

 and clover are "winter killed," as we say, and whole forests 

 die after an exceptionally dry summer followed by an unusually 

 severe winter. 



A sudden freshet may wash away in immense numbers the 

 season's crop of seeds of maple, elm, or oak, and send them 

 downstream to rot in the lowlands. The same freshet may kill 

 a valuable lot of mature timber downstream and change forever 

 the flora of the locality. 1 



A wet summer may drown most of the bumblebees, and then 

 the farmers need have small expectation as to the crop of clover 

 seed, which is dependent upon bees for fertilization. 



A late fall may so stimulate growth in peach trees and other 

 tender plants as to prevent that " ripening " of the wood neces- 

 sary to a successful endurance of extreme cold. On the other 

 hand, a "warm spell " in winter may start the buds, after which 

 a " cold snap " will kill outright in a day the prospective crop 

 of the year. The apple crop is occasionally lost by late cold 

 weather after M setting " of the young fruit. Of course this 



1 When the Chicago drainage canal was dug, many bodies of timber along 

 the banks of the Illinois were killed by the new water level established, and 

 many damage suits resulted. 



