398. Part IV. Chapter 2. 
Mimulus ringens willows (Salixco rdata, lucida, amygdaloides), Onoclea sensibilis 
and other ferns. The species are always somewhat mixed, but in each asso- 
ciation some one tall species is clearly predominant. Sagzttaria rigida, nearest 
the open channel gives place to S. Zarifolia mixed with Zizania aquatica and 
Sparganium. Following this a broad horizon of Scirpus lacustris, then S. fuvia- 
tlis mixed with Scirpus lacustris, which soon increases to a second broad 
circumarea mixed this time with some Sparganium eurycarpum. Sparganium 
in places is mixed with Pontederia cordata, Sagittaria; beyond the border of 
Scirpus lacustris which encircles this bed of Sparganium is a bed of Typha 
latifolia associated with Naias, Dianthera, Stum, Asclepias incarnata. Beyond 
the Typha is a vast stretch of Phragmiites communis occupying shallow water 
or exposed muddy places. 
The State of Michigan is characterized by the great number of deep 
hollows, slight depressions and flat areas in and upon which water accumu- 
lates and drains away very slowly. Thus lakes, swamps and bogs are numerous, 
“the swamps and bogs arising by the encroachment of vegetation upon shallow 
lake basins. If the history of the vegetation extends back to the period when 
a boreal type of flora was prevalent in the region, then a sphagnum bog is 
found. If the filling of the lake basin is subsequent and began when a more 
modern flora influenced the character of the invasion then a true swamp area 
has arisen. We frequently find as at Mud lake in Washtenaw County a small 
area held by bog plants while the shores of the rest of the lake, south, south- 
east and northwest are occupied by a sedge mat in which 7ypka latifola, 
Sagittaria latifolia, Peltandra virginica, Symplocarpus foetidus are most promi- 
nent. The bog areas of such lakes will be briefly discussed under bogs. The 
zonation of the swamp area of Mud Lake has been discribed by C. A. Davis’). 
Strand Formation. The shore line of western lake Erie?) is either sand or 
sandstone and the characteristic plants are Euphorbia polygonifolia, Triodia 
(Triplasis) purpurea, Elymus canadensis, Cenchrus tribuloides, Salır spec., Cakile 
and Polanisia graveolens. Many rock plants are subject to wave action. 
The plants of the drift, or middle beach, along Sandusky Bay and Lake 
Erie are such annuals as can endure the summer environment. Perennials and 
biennials are not found because of the destructive effect of ice and wave action 
during the winter. The characteristic species are Cakile americana, Xanthium 
canadense, Strophostyles helvola and the above named Polanisia, Cenchrus and 
Euphorbia. 
Along the entire eastern shore of Lake Michigan, the dominant plant of the middle beach 
is Cakile americana (= C. edentula) associated with Corispermum hyssopifolium, Euphorbia poly- 
gonifolia. The flora of the upper beach is much richer than that of the middle beach?). 
ı) In PEAT, Report State Board of the Geological Survey of Michigan 1906: 139. 
2) Peters, A. J.: The Plants of western Lake Erie. U. $. Fish Commission Bulletin 1901: 
57—79- 
3) Cowıes, H.C.: The ecological Relation of the Vegetation of the Sand Dunes of Lake 
Michigan. Botanical Gazette XXVII: 167—173. £ 
