INVASION OF A MISSOURI RIVER ALLUVIAL FLOOD PLAIN 1 99 



SUMMARY. 



i. The invasion of an alluvial bank formed by the Missouri 

 river, near Peru, Nebraska, was studied during August and Sep- 

 tember, 1916. 



2. The soil of this bank consisted of a mixture of very fine 

 sand, silt and clay. 



3. Deep cracks occurred frequently in the clayey part. Vauch- 

 eria and diatoms often grew on the moist, shaded walls of these 

 cracks. 



4. The agents of invasion were water, wind and possibly under 

 certain conditions, birds and other animals. 



5. The first plant, usually, to grow on the new land was a 

 Riccia . 



6. Seeds and fruits, deposited with the brush at the water 

 levels as the flood water receded, formed well-defined zones. 



7. As the water receded from the level areas, seeds and fruits 

 were left scattered on the wet soil, giving rise to a very open form 

 of vegetation. This open vegetation was broken in places by piles 



