PRETz: FLORA OF LEHIGH COUNTY, PENNSYLVANIA 51 
Glaciation, which has had such a marked effect on the flora of 
the corresponding region eastward, principally in New Jersey, is 
absent from the county. The extensive boggy areas characteristic 
of that region are not represented and many of the northern species 
found in association in these areas do not occur here. 
The terminal moraine, where it crosses the Delaware River near 
Belvidere, New Jersey, and the Kittatinny Mountains a few miles 
west of Delaware Water Gap, is only about twenty miles distant 
from the county, and the proximity of the great ice sheet of the last 
glacial invasion must have had its influence on the flora of the 
county, or at least that portion lying within the Great Valley. 
It would appear to a certain extent from its position that 
Lehigh County is so placed as to include within its boundaries 
many normally “southern” and ‘‘northern’’ plants. It is true 
that on account of these extensions the flora of the county is rich 
and that some species apparently have their limit of extension 
within the county, but it is doubtful whether Lehigh County 
equals in number of species any of the counties that bound it, 
with the possible exception of those to the north. This is an 
inference due to a review of some of the factors influencing the 
flora of this region, which have been briefly sketched. Thus, 
Berks, Montgomery, Bucks, and Northampton counties include 
within their boundaries many of the species of typical association 
in the mountains to the northwest, principally along the Delaware 
and Schuylkill rivers. All of these counties excepting Northampton 
are rich in extensions of Carolinian flora, which extends well up 
the river valleys. Northampton County shares with Lehigh the 
Lehigh River, and in addition its flora is enriched by the addition 
of a number of species associated with the glaciated region, be- 
sides such species as find their way into that county along the 
Delaware River. Whether the position of Lehigh County is 
unique with reference to the flora of the region when compared 
with these bounding counties will best be proven by future records. 
It has seemed sufficient to the writer to merely indicate such a 
possibility. 
Lehigh County is probably represented in the older collections, 
but it might prove difficult to confirm some of the older records 
