UNDER THE APPLE-TREES 



cannot repeat the genesis of living matter without 

 the aid of other living matter. The cows in the pas- 

 ture crop off the tender shoots of the young red- 

 thorn and apple-trees, and thus increase the strug- 

 gle of the sapling to become a tree. They do not 

 eliminate it; they retard its growth and add to its 

 toughness. 



All these considerations illustrate how living 

 things straggle with and against one another and 

 survive. All the grasses and the herbs of the field 

 struggle in the same way. If they are exterminated, 

 it is usually by fire or by flood, or by protracted 

 drought, or other elemental agencies. But not al- 

 ways. The chestnut blight which has lately attacked 

 our chestnut- trees threatens to exterminate the 

 whole race; the potato-beetle would doubtless, if left 

 alone, exterminate the potato; the currant-worm, 

 exterminate the currant; but these pests would 

 not be factors in developing new species. There 

 would be no survival of the fittest; all would go. 

 With the myriad forms of life that have become 

 extinct during the geologic ages, doubtless similar 

 agents were at work; enemies or unfavorable con- 

 ditions, or some mysterious failure in the springs 

 of life, have led to their disappearance. Natural 

 selection has played no part. Adaptation implies 

 adaptability something fluid and mobile which 

 is characteristic of life. Osborn says that certain 

 characters are adaptive from their first appear- 

 286 



