THE DUNES OF LAKE MICHIGAN 209 



sopifolium and Lathyrus maritimus to grow on this shore. So 

 we have seen that the stucty of the beach-flora of Lake Michigan 

 is interesting from a double point of view. It is especially fit 

 to make one feel, that halophytes and xerophytes are in reality 

 similar adaptations. 



I cannot close these notes on the beach-flora of Lake Michi- 

 gan without calling attention to one very characteristic feature 

 of the beach itself. I mean the line of driftwood, marking the 

 upper limit of the middle beach, which is absolutely missing in 

 my native country. It tells us on the one hand how rich the 

 American country still is in primeval forests. We saw plenty 

 of them ourselves. But on the other hand it shows how very 

 prodigal Americans have been of their woods until now. So 

 much wood has recklessly been cut in the forests on the moraine 

 near Lake Michigan that large quantities of it could escape from 

 the sawing-mills along the rivers and float to the lake without 

 attention being paid to it. And one feels inclined to warn, to 

 warn for the future, when all those forests will have disappeared, 

 climates will change and no wood for human purposes will be 

 available. Time has now come for a wise and economical man- 

 agement of American forests, as we have long known to be 

 true for our European ones. 



We now come to the second above mentioned point of differ- 

 ence between the dunes of Lake Michigan and those in Holland, 

 that is connected with the freshwater character of Lake Michi- 

 gan in contrast with that of the salt North Sea. We have al- 

 ready said that it is concerned with the quantity of lime in the 

 soil. 



As the water of Lake Michigan is fresh, it does not hide the 

 enormous numbers of testaceans, that are usually present in 

 salt water and of which we find the shells in heaps on the strand. 

 Hence the diluvial sand, that builds the dunes of Lake Michigan, 

 must be very poor in lime. The sand of our dunes on the con- 

 trary is, as a rule, very rich in lime and generally contains 3-4% 

 of it. On the windward slopes of the fore-dunes the percentage 

 can be much higher and rises to 12 or even 29%. Only in very 

 old dunes, mostly situated far away from the sea, has the lime 



