1899] DUNE FLORAS OF LAKE MICHIGAN 2: $05 
and Prunus Virginiana. With these shrubs young trees of Zila 
Americana are common. A lee slope thicket of Cornus, Tilia, 
and others of the above plant species is shown at the upper left 
hand of fig. ro. 
All of the species named above occur on arrested lee slopes” 
along the entire coast. The species which are peculiarly char- 
acteristic of such habitats are Cornus, Prunus, Equisetum, and 
Asclepias. These four species are found in other associations, 
but reach a decided climax here. Ammophila, Calamagrostis, 
Corispermum, Salix (both species), Vitis, and Tilia are almost 
‘common, but have a much wider habitat range. Ammophila, 
Calamagrostis, and Corispermum are also found in nearly all 
plant societies thus far discussed, but they disappear entirely as 
“oon as the vegetation becomes dense. The willows are common 
mmany places on the beach and complex, but they too are ruled 
out as soon as a real forest vegetation gets a start. Vitis grows 
also on rapidly moving Iee slopes, and remains after the forest 
has begun. Tilia more than all others looks to the future; as 
will soon be shown, it is the dominant tree of the first forests 
that grow on the old lee slopes. With the entrance of the bass- 
Wood, the true dune conditions and the true dune plants are 
obliged to Bake away. 
Cra other interesting plants that get an geese pi 
8 — lee slopes. At several such places a rae 
ay i. ula papyrifera was seen. . Near Chicago this Hs 
ea on the dunes at all, although common along pee 
i "ag It appears to become sore 
the ees the same is true of Thuya occidentalis. eat 2 
ic conditions northward are such as to permit plan's 
~ STOW normally j : ; row where the 
Xposure ig ally in protected situations to g pages He 
Where aa greater. Onan arrested dune at en se 
Gtiees , : for some reason are infrequent, Sp is 
with the hes ai laevis, and Achillea Millefolium grow a un 
Before Ang Previously mentioned. : 
; cing the further growth of vegetation on 
Somet Pn 
hing May be said of the origin and development of vegeta 
lee slopes, 
