506 CHARLES A. DAVIS 



decomposition, becomes exceedingly offensive in odors devel- 

 oped, and calcium carbonate crystallizes out on the bottom and 

 sides of the containing vessel, while the succinic acid disappears, 

 gas, possibly carbon dioxid, being given off more or less abun- 

 dantly. Whether these changes takes place on the outside of 

 the living plants, in the cell walls, or in the water surrounding 

 the plants has not yet been determined. 



Sufficient evidence is here presented, however, if the writer's 

 conclusions are correct, to show that the plants under discussion 

 are active agents in the concentration of calcium salts in the 

 fresh water lakes of Michigan, and that they alone have pro- 

 duced a very large part of the marl which has accumulated m 

 these lakes. It seems probable also that the principles devel- 

 oped by these studies are of very wide application in working 

 out problems presented by formations developed under similar 

 conditions elsewhere. 



Charles A. Davis. 



Alma College, 

 July 1, 1901. 



