PIONEER PLANTS ON A NEW LEVEE 42; 



PIONEER PLANTS OX A NEW LEVEE— IT. 

 FRANK E. A. THONE. 



A year ago the writer presented before the meeting of the 

 Academy at Iowa City a paper under the above title 1 describ- 

 ing the vegetation appearing during the first growing season 

 on a newly built embankment in Des Moines. It was his in- 

 i< nt ion to make this the first of a series of studies following 

 the development of the flora on this area until a permanent 

 balance of power had been established. 



Unfortunately, however, several circumstances intervened to 

 prevent the carrying out of this plan. The writer was able 

 to visit the area only a few times after the completion of the 

 first paper, and the information gleaned on these flying visits 

 covers only the most salient facts. In the second place, the 

 river itself has made a number of changes in the terrain. The 

 level space that originally lay between the foot of the embank- 

 ment and the edge of the channel has been entirely eaten away, 

 and in one place a portion of the levee itself has slid into the 

 river. On the opposite shore the erosion has been even more 

 rapid ; the entire face of the sand heaps described in the pre- 

 vious paper has disappeared, and on the continually slipping, 

 almost perpendicular wall of sand that remains no living thing 

 has so far been able to establish a foothold. And since the two 

 bridges which formerly connected the newly made island on 

 which these sand heaps lie with the mainland have been de- 

 stroyed, the reverse slopes are as much of a terra incognita as 

 the other side of the moon. Finally, the western end of the 

 Levee lias been graded and everything there is reduced to hopeless 

 chaos. 



There remains, then, only the actual embankment of the 

 Levee proper in anything like its original shape, and here alone 

 conditions have taken their normal course, so that it is only on 

 this part of the entire original area that any observations at all 

 were worth while. 



] See Iowa Academy of Science Proceedings, Vol. XXII, p. 135. 



