44 Bulletin Wisconsin Natural History Society [Vol. 12, Nos. 1 & 2 
surrounding or in close proximity to the tamarack grove. The 
coulee at this point is about one mile wide. The flat area here is 
wider than at any other point along the creek. The stream is 
small. A mile below the valley narrows. The soil in proximity 
to the tamarack marsh is very rich. All evidence seems to show 
that we had here an ancient lake which has to a large extent been 
drained. The region surrounding the grove is still very swampy, 
but there is no evidence anywhere of a typical sphagnum bog 
with its accompanying plants like Sarracenia purpurea, Drosera 
rotundifolia and Pogonia. . . . The tamarack swamp is a 
typical forest island; the seeds were undoubtedly carried by the 
wind from the LaCrosse valley” (Pammel, 1907, p. 87). Pammel 
thus seems inclined to the view that the ingression of the tamarack 
in these swamps was recent and from the north. 
A very few species of bog plants occur in the eastern United 
States in favorable, swampy localities in non-glaciated regions, but 
many of these swamps and marshes are of recent and, undoubt- 
edly, postglacial origin. Nor, on the other hand, does the biota 
of the glaciated areas at the extremity of the Wisconsin drift 
support the hypothesis that the biota of the Cassandra-Tamarack- 
Spruce Associations was driven far south. As a rule of biogeog- 
raphy it might be stated that in general, where physical and eco- 
logical changes are not sudden and abrupt egression is in the same 
order as ingression. Certain plants ingress a region in the form 
of a wave or migration from some center of dispersal; this ingres- 
sion may continue extensively for considerable time, or it may be 
short-lived; ultimately however it is dominated by the ingression 
of another association which may or may not come from the same 
direction as the former; if any plants survive from the first in- 
gression it will usually be those which last gained a foothold, be- 
cause they are the ones among all of the first ingression which have 
an ecological optimum most like that of the second ingression; 
the same is true of the animals of these succeeding ingressions. 
The biota of the bogs just within the southern extremity of the 
Wisconsin drift contains a few of the early ingressing bog plants, 
and two or three species of widely ranging bog animals; there are 
no relicts of those animals most typical of northern ‘Tamarack- 
spruce swamps” and many of the plants are. lacking. For example, 
I have been unable to find any published authentic records of the 
