Shafer : Vascular Flora of Allegheny County. 23 



* A. dentata (Torrey). Toothed rock-cress. 



Neville Township, south shore of island, May 3, 1890 ; O'Hara 

 Township, river bank near Ross Station, May 9, 1900. 



* A. laevigata (Muhlenberg). Smooth rock-cress. 



* A. laevigata Burkii Porter. Burk's rock-cress. 



* A. Canadensis Linnaeus. Sickle-pod. 



f A. glabra (Linngeus). Tower mustard. 



A. perfoliata Lamarck. 



DRABA Linnjeus. 



* D. verna Linnaeus. Whitlow-grass. 



KONIGA Adanson. 

 AL YSSUM Tournefort. 



* K. maritima (Linmieus). Sweet alyssum. 



Sewickley, "ashery," foot of Walnut street, August, 1892. 

 Spreading ! August 10, 1897. 



RORIPA Scopoli. 

 NASTURTIUM R. Brown. 



f R. Nasturtium (Linnaeus). Water-cress. 

 N. officinale R. Brown. 



* R. palustris (Linnaeus). Marsh-cress. 

 N. palustre De CandoUe. 



* R. Armoracia (Linnaeus). Horseradish. 



BARBAREA R. Brown. 



* B. Barbarea (Linnaeus). Common winter-cress. 



B. vulmris R. Brown. 



