DUNE FLORAS OF LAKE MICHIGAN 363 
sfytDesplaines bottoms; two of the remaining four, 
%q:nd Smilacina, are common as mesophytes. Only 
tim fifteen, Rhus Canadensis, and Rosa, are commonly 
ppare ‘ntly the life conditions on the basswood dunes are 
ut similar to those of the river bottoms. The former 
| appear toh be xerophytic, the latter mesophytic and inclining to 
tydrophy tic. The soil of the dunes is sand with scarcely any 
fativer bottom flora. At the south end of the lake, at least, 
the basswood dunes and river bottoms are separated from each 
; her by many kilometers. The likeness of the floras suggests 4 
| ikeness of conditions in the two apparently very dissimilar hab- 
. What this likeness is, if it exists at all, cannot easily be 
n 
Itis this river bottom flora on the dunes that furnishes the best 
“amples of anatomical variation due to habitat conditions. Most 
pte gross variations are found in the leaves of nearly all 
aes Celtis, a tall tree on the bottoms, is a horny 
% to on the dunes. The tissues, also, are highly modified so 
ig the requirements of the dune conditions. These 
tons not alone in a single species, but in a aa 
un : ES ported, as it were, from the river bottoms to the 
: Supply a large part of the material for the second or 
. perion of this paper. It is also the author’s inten- 
. *Xpetiment with the river bottom and dune forms of the 
cia and endeavor to determine whether or not these 
The nay take place within a single plant gen o 
the Stee oo bment of an undergrowth of shrubs an ee 
itg of : 4Sswood dunes tends more and more to stop : oe 
* sand between the plants. The partial decay ° : 
Vari 
tha; 
