Xo. 14.] FLOWERING PLANTS AND FERNS. 405 



Arctium minus (Hill) Bernh. (smaller). 

 Arctium Lappa L., var. minus Gray. 

 Arctium Lappa L., var. tomentosum Gray. 

 Arctium tomentosum of Britton's Manual in part. 

 Common Burdock. 



Common. Roadsides and waste places. July — Oct. 

 Naturalized from Europe. A form with woolly involucral 

 bracts sometimes occurs. 



CARDUUS L. Plumeless Thistle. 



Carduus acanthoides L. (like Acanthus, the Bear's-breech). 

 Curled Thistle. 



Rare. Waste ground: Sahsbury (Mrs. C. S. Phelps). 

 July — Aug. Fugitive from Europe. 



CIRSIUM Hill. Common or Plumed Thistle. 



Cirsium lanceolatum (L.) Hill (lance-shaped). 

 Carduus lanceolatus L. 

 Cnicus lanceolatus Willd. 

 Common or Bull Thistle. 



Frequent. Roadsides and pastures. July — Sept. Natural- 

 ized from Europe. 



Cirsium spinosissimum (Walt.) Scop, (very spiny). 

 Carduus spinosissimus Walt. 

 Cnicus horridulus Pursh. 

 Yellow Thistle. 



Occasional in fields and borders of salt marshes along tlie 

 coast. June — July. 



Rarely occurs with purple flowers. 



Cirsium discolor (Muhl.) Spreng. (of different colors). 

 Carduus discolor Nutt. 

 Cnicus altissimus Willd., var. discolor Gray. 

 Field Thistle. 



Fields and thickets. Occasional in most sections, but fre- 

 quent to common along the coast and throughout the Housa- 

 tonic Valley. Aug. — Sept. 



Flowers sometimes white. 



