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 measured 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 w'ere 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 societv 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 about 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 re.sult is more and 
more of a mixed societv. 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 ninet^■-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 societv, how'ever, 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 vigorously 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 tr}" the experiment of the juvenile stage. 
