113 



this association and the grassy sand plain. This later asso- 

 ciation is composed of over 90% of Poa compressa, which, how- 

 ever, does not grow sufficiently thick to prevent the sand from 

 giving the color tone to the area. Secondary species appear 

 scattered throughout, but they are never of much importance, as 

 they occur only as individuals here and there in the grass. 

 Some of the most frequently occurring secondary species are : 



Euphorbia coroUata, 

 Verbena hastata, 

 Erigeron canadensis, 

 Verbascum thapsus, 

 Cacalia tuberosa 

 Monarda punctata, 

 Pycnanthemum virginicum, 

 Panicum (fpseudopubescens), 

 Isanthus brachiatus, 

 Engercm divaricatus, 



Poa pratensis, 

 Rumex acetosella, 

 Achillea millefolium, 

 Anaphalis margaritacea. 

 Oxalis stricta, 

 Lobelia spicata, 

 Scutellaria parvula, 

 Hypericum kalmianum, 

 Potentilla a/rguta. 



The most important secondary species of this association from 

 the view-point of this article are Juniperus horizontaUs and 

 Juniperus communis depressa, because they are the only sec- 

 ondary species that can form relic dunes. There are a few 

 mats of each of these junipers at intervals in the sod. These 

 together with the Jimcus balticus littoralis are the only species 

 which, in this region, are instrumental in the formation of 

 relic dunes. 



With this brief consideration of the physiographic appearance 

 of the region and the plant associations which occupy it, the 

 steps in the formation of the relic dunes are now in order. In 

 places where in every storm, not merely the more violent ones, 

 the waves attack the bjuff, sooner or later passageways or 

 rifts will be cut thru the Juncus association. This allows un- 

 dermining of the sand plain, whose surface is sparsely covered 

 with vegetation, the roots of which have but a very limited sand- 

 binding capacity. Consequently the plain is washed away as 

 far as the waves have power. A few of the stages that follow 

 are shown in the accompanying plate, in which the structure 

 of the surface is shown on the left, and on the right selected 

 profiles have been constructed. 



The sand from immediately to the landward of the Juncus 



