210 THEO. J. STOMPS 



disappeared from the superficial layers of the soil. It has been 

 dissolved by rainwater containing carbonic acid and by the influ- 

 ence of humus substances. In this way the soil of these old 

 dunes has regained the properties of a normal diluvial soil, as 

 it is found in those parts of Holland that are covered by heath. 

 Only here such typical calciphobous heath-plants as Pteridium 

 auilinum, Juniperus communis, Empetrum nigrum, Ilex aquifo- 

 lium, Genista anglica and G. tinctoria, Calluna vulgaris and Erica 

 tetralix may be met with and they do not occur on the lime- 

 containing sand of the younger dunes. If we now revert to our 

 discussion of the dune-floras of Lake Michigan, we can not ex- 

 pect to find here something like the succession just described. 

 In fact lime is missing everywhere in the soil of the dune-region 

 and the visiting botanist can gather this immediately from the 

 composition of the flora. Everywhere his eye discovers species 

 that are known to be more or less calciphobous. An interesting 

 example that we found growing at Miller, Indiana, quite near to 

 the Lake, is e.g., Pteridium aquilinum. This species is surely 

 one of the most strictly calciphobous known and is nowhere to 

 be found in our lime-holding dunes. Another example, also seen 

 near Miller, Indiana, in the pine-dune-association, is Juniperus 

 communis. This species passes for not so typically calciphobous 

 as Pteridium aquilinum is. Still in our dunes it behaves as such 

 and is strictly limited to the heath-covered parts, not being able 

 to grow elsewhere. At Lake Bluff, Illinois, especially it showed 

 to us with certainty, that even in young dunes no lime can be 

 present in the soil. It was growing there almost on the beach, 

 e.g., near the entrance of the ravine, in which we saw Thuja 

 occidentalis in abundance, and on the third row of the miniature 

 dune area, which somewhat farther to the north, has drawn our 

 attention. So this second example turns out to be still more 

 instructive from our point of view than the preceding one. 

 More instances can easily be cited, but I believe that my argu- 

 ment has been sufficient to show, that the freshwater character 

 of Lake Michigan causes indeed a second fundamental point of 

 difference between the dunes surrounding this Lake and those 



