IOWA ACADEMY OF SCIENCES. 
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585. 8. palustris (L.) Hook. Occasionally appearing in 
marshes and around lakes. 
Arctium L. 
586. A. lappa L. Burdock. Waste places; introduced 
from Europe. 
Cnicus L. 
587. C. iowensis Pammel. Our commonest thistle; 
woods and prairies. 
588. 0 . ioivensis crafty i Pammel. Woods and prairies; 
less common than the species. For a descrip- 
tion of this and the preceding, see Proc. Iowa 
Acad. Sciences, VIII, p. 231. 
589. C. canescens (Nutt.) Pammel. (G. undulatus var. 
canescens Gray; Cirsium canescens Nutt.) A per- 
ennial thistle growing in patches, and becoming 
more plentiful. 
590. C. lanceolatus (L.) Willd. ( Carduus lanceolatus L.) 
Common Pasture Thistle. Fields and waste 
places; naturalized from Europe. 
