Liriodendron tulipifera. 
Acer saccharinum. 
Acer rubrum. 
Fraxinus nigra. 
Fraxinus americana. 
Juglans cinera. 
Ulmus americana. 
Ulmus racemosa. 
Platanus occidentalis. 
Lindera benzoin. 
Xanthoxylum americanum. 
Pilea pumila. 
Urticastrum sp. 
Thalictrum dasycarpum. 
We have in the cedar swamp a formation of plants of a decidedly boreal 
aspect, maintaining itself, but for the influence of man, in the midst of a 
flora predominantly southern. Ability to maintain itself in the struggle with 
the southern flora was probably due originally to differences in the habitat. 
Just what the factors are that make hog conditions unsuitable for the growth 
of most plants have not been fully determined; but some combination of 
edaphic conditions permitted the northern plants to remain and removed 
them very largely from competition with the southern forms. In the later 
stages of the development of the bog, many of these conditions have probably 
been modified or removed. Many of the southern plants could undoubtedly 
maintain themselves under the present conditions; but the bog plants have 
such complete possession of the habitat that invasion is practically pre- 
cluded. But for the influence of man, the formation would no doubt have 
been able to maintain itself for many centuries to come. 
About two miles southeast of Richmond, Ind., lies a small remnant of 
a formerly much more extensive peat bog. It is known as the Elliott’s Mills 
bog and is in such an advanced state in the physiographic cycle of bogs that 
little resemblance to a typical bog remains. But the characteristic peat 
soil and the presence of certain bog and boreal plants indicate its former 
character. The bog lies in a broad, shallow valley between morainic hills. 
It evidently occupies a shallow, undrained depression scooped out in a softer 
part of the underlying Niagara limestone. The bog is crossed by a public 
