MICHIGAN ACADEMY OF SCIENCE. 
55 
INVADING SPECIES. 
Iris versicolor. LysimacJiia terrestris. 
PotentiUa anserina. Campanula uliginosa. 
Eupatoriuin perfoliatum. Campanula aparinoides. 
The J uncus halt ic us littoral is Association. 
This association of the lake beaches is represented in the region very 
scantily, on a few of the tongs of sand which projected out into South 
Fishtail bay, by a sprinkling of plants of the dominant species J unous 
balticus littoral is. As a general thing, the J uncus is between the Heir pus 
americanus and the PotentiUa anserina, showing succession into the 
former and giving way to the latter. Occasionally, however, on a very 
few of the stations there is no other vegetation between it and the open 
water. The severe ice work along the shore each winter is undoubtedly 
a potent factor in reducing the extent of this association in this region, 
for otherwise, conditions seem entirely suitable for it. 
The PotentiUa anserina Association. 
This association of lowland plants, which in some localities quite 
extensively covers the beach, is extremely poorly represented in the 
region. In a few places a mere fringe of the dominant species at the 
foot of the fringing dune or ice-work bluff is all that there is to indicate 
the presence of this association of plants. In a few other places where 
the beach is very gently sloping and protected from severe wave action, 
the presence of a number of these plants mixt in with Ecirpus americanus 
and Eleocliaris palustris vigens indicates the presence of the association 
in the midst of rapid successions. Here the Potent ilia grows from the 
water level up as far as other plants will permit it to grow. Sub- 
mergence, however, cannot be withstood. In certain places, where this 
association develops around beach pools it serves to catch the seeds 
of bog trees, as Acer nibrum and Thuja occidentalis. In other places 
grasses, Elgmus canadenis and E part in a michauxiana , obtain a start and 
a low dune may be formed. 
List of the Species of the PotentiUa anserina Association: 
DOMINANT SPECIES. 
PotentiUa anserina. 
SECON DA II Y SPECIES. 
Soli dago gra m i n ifolia. 
RELIC SPECIES. 
Ecirpus americanus. J uncus balticus littoralis. 
Eleocliaris palustris vigens. 
INVADING SPECIES. 
Acer nibrum (seedlings). 
Thuja occidentalis (seedlings). 
Elgm 1 1 s ca na dens is. 
E pa rt inn m i ch a uxia n a . 
