﻿486 Porter : The Flora of 



In the first section of the route from Duncannon, the river 

 flows majestically through a mighty gap in the Blue Mountain 

 and its parallel ranges. On the east side of it lies Dauphin County 

 and on the west Perry, south of which Cumberland is reached and 

 then York lower down. Below Dauphin comes Lancaster, and 

 these two counties have their western boundaries at low-water 

 mark on the opposite shores, so that all the islands are included 

 in their territorial limits. 



At Falmouth the river enters the region of the South Moun- 

 tain system, and along its whole course down to the Maryland 

 line is bordered by bold bluffs and high ridges, intersected by 

 numerous ravines. 



The conditions here described are all favorable to a rich and 

 diversified flora, and such it, indeed, is. The denizens of the 

 mountains and the interior find pathways toward the sea. For 

 whilst not a few of the plants enumerated have crept up from 

 lower levels, a greater number appear to have come down from 

 higher altitudes, or from the remote western sources of the mighty 

 river. About thirty species of the list belong naturally to the 

 region beyond the Alleghenies, through which the west branch 

 of the Susquehanna finds a passage, drawing its first waters from 

 almost the same levels as streams that descend into the basin of 

 the Ohio. On the other hand, about twenty seem to have been 

 conveyed down from the elevated mountain -plateaus, drained by 

 the tributaries of the Xorth Branch. 



LIST OF SPECIES AND THEIR STATIONS. 



PTERIDOPHYTA. 



i. Onoclea Strutliiopu 



Safe Harbor ; McCall's Ferry. 



Islands, near Harrisburg and 



Asplenium angustifolium Michx. York County, opposite 



Marietta 



: 3. Asplenium montanian Willd. York County, opposite Mari- 

 etta ; ravine at York Furnace ; mouth of the Tucquan. On roc » 

 4. Asplenium pinnatifidum Nutt. Ravine at York Furnace 

 and on rocks above the mouth of the Tucquan, 



