March, 1905.] Struggle for Life on a Sandbar. 3°3 



smaller dead and decaying individuals. Going a little farther 

 toward the centre of the field, two hundred plants (Cottonwoods, 

 Peachleaf Willows, and Sandbar Willows) were counted on an 

 accurately measvired square foot! Many, however, were losing 

 in the struggle for space and light and were either sickly in 

 appearance or in a dying condition. A few were already dead. 

 The smaller ones were hopelessly shaded. A great destruction 

 was taking place among these immature or juvenile individuals 

 long before the normal conditions of adult life were possible. 

 All had apparently sprouted at about the same time and the 

 struggle for existence was among more or less similar individuals 

 of a very few species. These possessed the ground so completely 

 that there was practically no opportunity for an intruder to gain 

 a foothold at this stage of the process. 



But suppose that this society were to continue its develop- 

 ment for a number of years or until the trees had grown to 

 maturity. In three years there would be abotit one tree for each 

 square foot. Such examples are numerous on old sandbars. Of 

 the two hundred plants one hundred and ninety-nine would have 

 no room and must inevitably perish. But in this way space is 

 again made available for other plants to sprout among the sur- 

 vivors. Thus the original struggle among those of like nature 

 makes an opportunity for plants of other species to invade the 

 territory. Some of these can endure the shade and other 

 imposed conditions already present and the result is more and 

 more of a mixed society. The struggle for life is now between 

 diverse species under all gradations of favorable and unfavorable 

 conditions. The struggle among the original possessors of the 

 soil is, however, not yet at an end. As the trees grow larger more 

 and more must give way to their more powerful or fortunate 

 neighbors. In twenty-five years there would be at most but one 

 large Cottonwood or Willow for each fiftv square feet. Nine 

 thousand nine hundred and ninetv-nine little Cottonwoods and 

 Willows will have been over-reached and over-shadowed and the 

 one solitary giant will stand as the sole survivor of a conquered 

 multitude. 



Not a single plant of this particular society, however, was 

 thus fortunate. For two years later a high flood washed over 

 the entire bar and removed everv vestige of the thriving young 

 plant society. Accidental destruction put an end to the process 

 of the elimination of the unfit. At present the struggle for 

 existence is again going on as vigorouslv among the members of 

 a new society as it did among those which had occupied the soil 

 before ; and it is evident that without the destruction of the pre- 

 vious society the later generation would not even have had an 

 opportunity to try the experiment of the juvenile stage. 



