1899] DUNE FLORAS OF LAKE MICHIGAN 365 
leaves which fall year after year gradually produces a humus. 
The conditions approach more and more those of the typical 
mesophytic forest, even though xerophytic dune societies may 
surround on every side. The growth of the humus permits the 
(evelopment of a low vegetation, consisting of lichens, mosses 
and forest herbs. The vegetation, shade, and humus conserve 
the water and cause a mesophytic soil in spite of the slope and 
sand, Seedlings of other trees, yet more indicative of the shady 
mesophytic forests than the basswood, make their appearance. 
The most prominent of these is the sugar maple, Acer sacchari- 
mun, Scarcely less important are the beech, Fagus ferruginea, 
aid the hemlock, Zsuga Canadensis. These trees produce the 
densest shade and cause the extermination of the basswood and 
its associates. Each vegetation from the original Ammophila to 
the maple forest, therefore, gives a denser shade than the one 
preceding, 
Accompanying the above-named trees are such typical meso- 
Phytic forest herbs as Hepatica triloba, Trillium grandiflorum, 
Fhiphegus Virginiana, and Arisaema triphyllum. That the condi-+ 
liots not only in the soil but even in the air are less xerophytic 
than when the basswood was the dominant tree is shown by the 
breat luxuriance of the vegetation. The trees are just as large 
*m inland forests and the xerophytic structures that were 
Present in the basswoods and their associates are quite absent in 
= maples, beeches, and hemlocks. The air seems to be almost 
E thiytic as in the inland forests. The maple and yt 
iz; a not frequent on old dunes at the south ne ma 
. = a ee ye fet te one . tic for- 
i i this Tegion as they are in Michigan. wade Hie 
Basis 4 dunes were seen at Saugatuck, ran ‘ ot 
et é » and Charlevoix. At Frankfort there isa pipe a. 
Obed as ia Slope of an old dune which is as See a oo 
iy as. an inland location. At Chae. . se Aeaith ie 
time aii a pe eo ae metion mi te BS the dune. 
‘ © mesophytic flora could have existed 0 ae 
"esophytic forest is the most permanent of plant soc 
