Plate XVIII. 



Fig". 1. Windward margiti of the thickets on the nver dune, Hanover area. The outermost 

 tree at the left is a green ash. A small Pliysa/is hclcrophylla association in the foreground, at the 

 rig-ht. 



Fifr. 2. Dune thickets on the slope <>l lln- ii\ei ,liin.-, Haiicjvri ai.-a. I lie exposed root 

 system of the ash at the left indicates the mij^Maiion of the dune 



