956 REPORT OF STATE GEOLOGIST. 



AMBROSIACE^E. Ragweed Family. 

 AMBROSIA L. 



A. bidentata Michx. Lance-leaved Ragweed. 



Found only in the central and southern counties of the State. 

 Found in open places, either prairies or clearings. Prefers a rich, 

 loose soil. 



Flowers in August and September. 



Vigo and Clay (Blatchley); Gibson and Posey (Schneck); Put- 

 nam (MacDougal). 



A. trifida L. Great Ragweed Horse-weed. 



Abundant and widely distributed in all parts of the State. 

 The species reaches its highest development both as to numbers 

 and size in rich, alluvial soils subject to overflow. It also invades 

 cultivated fields and along their borders often forms a dense 

 thicket. 



Flowers from July until the frosts. 



Jefferson (J. M. Coulter); Monroe and Vigo (Blatchley); Fay- 

 ette (Hessler); Clark (Baird and Taylor); Dearborn (Collins); 

 Jay, Delaware, Randolph, and Wayne (Phinney); Franklin 

 (Meyncke); Gibson and Posey (Schneck); Noble (Van Gorder); 

 Putnam (MacDougal); Tippecanoe (Cunningham); Kosciusko; 

 Hamilton and Marion (Wilson); Steuben (Bradner). 



A. trifida integrifolia. (Muhl.) T. and G. 



Associated with the former in certain parts of its range, but 

 much less abundant and less widely distributed. As the preced- 

 ing, it has a strong vitality, growing up time and again from the 

 stumps left from cutting. 



Jefferson (J. M. Coulter); Jay, Delaware, Randolph, and Wayne 

 (Phinney); Gibson and Posey (Schneck); Franklin (Meyncke); 

 Vigo (Blatchley); Fayette (Hessler); Hamilton (Wilson). 



A. artemisiaefolia. L. Ragweed. Wild Tansy. 



The most abundant species of the genus in our bounds. It is 

 found in all parts of the State in waste places and cultivated 

 fields. While it frequently takes complete possession of fallow 

 ground and encroaches heavily upon cultivated areas, it is re- 

 garded by many farmers as beneficial to the land. I have been 

 unable to get any clear reason for this belief. It is certainly with 



