1920 Frye; on Plant Migration 897 



Summary 



1. Shore plants must migrate with the water level or perish when 

 the level falls permanently. 



2. Some make the change easily, others with difficulty. 



3. Erosion by waves is a factor in keeping some plants below a cer- 

 tain dejith in the water. 



4. Floating seeds are so general that it is doubtful whether this 

 characteristic is any considerable factor in determining the habits of shore 

 plants. 



5. The seeds of some thistles roll like tumbleweeds on smooth water. 



