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scant numbers and of small size in Lake, Porter and Laporte counties. 
This typical northern species may also be regarded as one that has 
retained a foothold in isolated localities after the recession of the shores 
of Lake Michigan and the disappearance of the bordering swamps. The 
reported occurrence of the species in Tippecanoe County (Golden) “in 
; 
sparing numbers along the Wabash River’ demands further study. The 
well-known difficulty of discriminating the species of Betula, due to sea- 
sonal and age changes in appearance and habits, suggests that a closer 
study may prove the reference an error. 
The Paper or Canoe Birch (Betula papyrifera Marshall) is found in 
Lake and Porter counties, always being reported as rare and of small size. 
This is another species definitely northern in its mass distribution, the 
Indiana stations standing as its extreme southern limit. It is probably 
another of the species which entered our area in the time of flooded rivers 
and lakes of the Champlain but one which has been able to maintain a 
precarious foothold up to the present time. Its early disappearance from 
the tree flora seems inevitable. 
The Tag or Speckled Alder (Alnus tneana (Linnzeus) Muenchhausen ) 
is found in Lake and Porter counties between dunes near to the lakes. 
This is the common alder found in swamps and on the borders of streams 
further north. It has been able to maintain itself in our area in greater 
numbers and with less reduction of size than any other one of these 
extreme northern species. 
A dwarf shrubby form of Hackberry (Celtis pumila (Muhlenberg) 
Pursh) is included. In both Gray and Sargent the form is regarded as a 
variety of C. occidentalis Linnzeus. Its general range is in the South 
Atlantic States ranging westward to Missouri, Colorado, Utah and Nevada. 
It has been reported only from Lake County hear the Calumet River at 
Millers. Its occurrence in such a restricted locality is rather puzzling and 
as yet no satisfactory explanation has been reached. The form in the 
greater part of its range occurs on rocky banks of streams—a condition not 
even approximated at its Indiana station. The temptation to regard it as 
an ecologic variant of the very common Celtis occidentalis is almost irre- 
sistible. 
Of the six species just discussed, five are definitely northern in their 
mass distribution. Their presence as members of our flora is very evi- 
dently referrable to the continuity of waterways existing during the 
