544 PROCEEDINGS OF THE ACADEMY OF [Oct. r 



Chester Group: 



Delaware County — 



1. Fawkes Run (Newtown). 



2. Preston Run. 



3. Bear Hill. 



4. Blue Hill. 



5. Middletown Township (Mineral Hill, Barrens~ofJ\liddle- 



town, Williamson, Lenni, Wawa). 

 Chester County — 



6. Sugartown Barrens and Serpentine Ridge. 



7. Cedar Barrens. 



S. West Chester Barrens (Fern Hill). 

 9. Sconnelltown and Strode's Mill. 



10. Brinton's Quarry. 



11. Marshallton (specimens noted collected by B. Long). 



12. Unionville. 

 State-line Group: 



13. Nottingham Barrens (Nottingham Station to Goat 

 Hill). 



14. A few other specimens, mainly collected by J. J. Carter, 



are cited from points in southern Lancaster County. 



Composition of Flora. 



Throughout these areas, and doubtless far beyond on either side, 

 the flora of the Conowingo Barrens is strikingly uniform, yet strik- 

 ingly in contrast with that of the surrounding district. The latter 

 originally was everywhere mesophytic woodland, on the Barrens 

 the change is made to a xerophytic woodland, and over considerable 

 areas to no woodland at all. Though other xerophytic areas, as 

 notably the South Valley and North Valley Hills to the north or the 

 dry sandy barrens of New Jersey across the Delaware River to the 

 south and east, lie not far away, the flora of the Conowingo Barrens 

 is quite distinct. 



Yet the flora of these barrens is not uniform. Situated like 

 islets in the midst of the surrounding vegetation, probably never 

 interconnected, it is interesting to note that species will occur and 

 be quite prevalent or even predominant on one, yet be quite scarce 

 or not present at all on another. This local variation is most pro- 

 nounced between the floras of the Chester and State-line groups. 



In the general sketch now presented only the features common 

 or nearly common to all the main exposures will be given. Local 



