520 PROCEEDINGS OF THE ACADEMY OF [Dec, 



FURTHER NOTES ON THE FLORA OF THE CONOWINGO OR SERPENTINE 

 BARRENS OF SOUTHEASTERN PENNSYLVANIA. 



BY FRANCIS W. PENNELL. 



Two years ago the writer published in the Proceedings of the 

 Academy of Natural Sciences 1 an account of the flora of the 

 Conowingo or Serpentine Barrens of southeastern Pennsylvania. 

 Effort was made, by field collections and herbarium-study, to 

 form a reasonably complete list of the characteristic species. At 

 that time, however, he had been unable to make full collections 

 during June, and collections made at this season during 1911 and 

 1912 have shown a considerable number of omissions. As col- 

 lections have now been made during every month of the growing- 

 season, and it is believed a practically complete view of the flora 

 gained, it has seemed advisable to thoroughly revise and emend the 

 list previously offered. 



In addition to his own and Bayard Long's collections of the past 

 two seasons, he has had the opportunity of reviewing the valuable 

 material of Albert Commons recently presented to the Academy. 

 The Serpentine specimens in this collection are nearly all from 

 Centerville, Newcastle County, Del. As this locality is now 

 threatened with extinction, we are fortunate in possessing some 

 record of its flora. 



In the preparation of these notes he has been much indebted 

 to Mr. Bayard Long, who throughout has given him most valu- 

 able assistance. He is also indebted to Mr. Eugene P. Bicknell for 

 verification of certain determinations in Agrostis and Car ex. 



As some of the locality names used do not appear on the local 

 maps, it may, though late, be of service to indicate by latitude 

 and longitude the location of each barren. Each area may 

 so be found either on the Philadelphia Geological Folio, where the 

 Serpentine areas are indicated in green and labelled "sp," or on the 

 Soil Survey of Chester County, where the more definite Conowingo 

 Barrens are indicated in yellow and labelled "Cb." 



1 Proc. Acad. Nat. Sci. Phila. (October, 1910), pp. 541-584. Issued January 13, 



