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lands frequently inundated during the year, or in low moist localities. We 
find that the larger part of them, in their mass distribution follow the 
swamps of the Atlantic or Gulf coast, or of both. It is very evident also 
that the extension of range northward must have occurred when similar 
physical conditions existed; that is, either at the time the Gulf of Mexico 
stretched an arm far into the north, or if a later date is preferred in the 
time of the flooded rivers and lakes of the Champlain period. Occasional 
meaus of transportation may serve to explain occasional cases, but where 
species become component parts of a forest in a region apparently remote 
from their mass distribution a different explanation must be sought. 
Six species, so far as the records go, are confined to Lake, Porter and 
Laporte counties or to some one of them. In this region, also, extremely 
skillful and persistent work has been done by Rey. E. J. Hill, a fact which 
should be taken into account. The species peculiar to this region are the 
following : 
Pinus Banksiana Lambert. 
Thuya occidentalis Linnaeus. 
Betula populifolia Marshall. 
Betula papyrifera Marshall. 
Alnus incana (Linnaeus) Muenchhausen. 
Celtis pumila (Muhlenberg) Pursh. 
The Jack or Scrub Pine (Pinus Banksiana Lambert) occurs in Lake 
and Porter counties, where it is fairly Common on the sand dunes border- 
ing Lake Michigan. The general range of this species is decidedly north- 
ern, the Indiana stations representing in all probability its extreme south- 
ern limit. In our area it is an undersized, rather shrubby form, maintain- 
ing itself with difficulty. The continuity of waterways is the evident 
explanation of the occurrence of this species in the Indiana tree flora, 
The Arbor-Vitee or White Cedar (Thuya occidentalis Linneus) appar- 
ently occurs native only in Lake County. This characteristic species of 
northern swamp regions is found only in cold swamps of our area. There 
seems no good reason why it should not be found in similar situations in 
other counties bordering Lake Michigan. The form has been so extensively 
planted for windbreaks and for ornament that many incorrect citations are 
on record. Its presence as a member of our flora is evidently referrable to 
continuous waterways furnished by the Great Lakes. 
The Gray or White Birch (Betula populifolia Marshall) is found in 
