48 



NATURE STUDY REVIEW [9 : 2— Feb., 1913 



Fku'ke (). — Dune advancing over a forest. The tops of partially buried 

 trees may be seen in the middle background. (Caldwell.) 



ly b}- ice action during the winter. No dtmes occupy this area as 



there is no vegetation to start them, and the wave and 



ice 



action are severe enough to destroy any that get started. The 

 second beU from the lake is occupied mostly by annual plants 

 and small dunes may be built here. Young cottonwood and sand 

 reed seedlings are common. The third belt includes the active 

 dune building area, and the characteristic plants are the sand reed, 

 cottonwood, dogwood, willow, balsam, aspen, and sandcherry. 

 The cottonwood, willow, and dogwood usually start in the wet 

 sand near the base of the dune and grow upward with the grow^th 

 of the dune, constantly keeping their upper parts open to the 

 light. When the dune becomes more stable and shade is cast by 

 the moving-dune plants, the pine seedlings are able to germinate, 

 ^nd the jackpine. whitepine, red cedar, and juniper become char- 

 acteristic. This stability leads to the fourth stage, as humus is 

 allowed to accumulate and oaks thrive. In the oak and pine for- 

 est may be fcuind such common plants as bearberry. grasses and 

 sedges, wild rose. New Jersey tea, i)rickly pear, mosses, straw- 

 berry, black haw. etc. It is evident, therefore, that four com- 



