206 THEO. J. STOMPS 



made towards the end of our excursion. I shall not do this, 

 however. Perhaps I can give proof of my indebtedness to Pro- 

 fessor Cowles best by showing that the beginning of his excur- 

 sion was already very interesting to me. Is it not a matter of 

 course that one whose native country could not exist if it were 

 not protected by dunes against the sea, felt especially attracted 

 by the study we made of the dunes of Lake Michigan? Let me 

 therefore say a few words about this region, which we visited 

 immediately after our excursion had started in Chicago the first 

 of August, and compare it with our Dutch dunes. Of course I 

 cannot enter into particulars and must confine myself to the de- 

 scription of some general impressions. 



The water of Lake Michigan is fresh and that of the North 

 Sea is salt. This stands to reason, but is important to him who 

 studies the flora of the adjacent territories, because it is con- 

 nected with differences in the chemical characters of the soil. 

 These differences are of two kinds. They bear upon the amount 

 of common salt in the soil on the one hand and on the amount 

 of lime on the other. 



Of course the shore of Lake Michigan does not contain any 

 salt at all. On our Dutch coast on the contrary salt in the soil 

 plays a considerable role in the development of the flora, not so 

 much in the dunes proper, but mainly on the middle and the 

 upper beach. Middle beach I call, in agreement with Professor 

 Cowles, that zone of the beach that lies between the high-water- 

 marks of summer-storms and winter-storms and is colonized only 

 by some annual herbs, because the possibility of survival through 

 the winter period is excluded. The upper beach, not even 

 flooded by the high storms in winter, presents the same species 

 and in addition to these many others, especially perennial herbs 

 with creeping rhizomes. As the middle beach is sometimes 

 washed by sea-water and the saline water in the soil lies at a 

 slight distance below the surface, as the air at the sea-side is 

 usually very rich in salt-particles and during low-tide often large 

 quantities of much salt-containing sand are blown landward 

 from the lower beach, it is clear that our strand at least must 

 bear a halophytic vegetation. It is generally known, that this 



