WEEDS OF MONTANA. 



27 



10. AMBROSIA TRIFIDA, L. Horseweed; Tall Ragweed. 



A large annual with opposite 

 three-lobed leaves and flowers 

 very similar to the two above. 

 It is here rarely more than two 

 or three feet high, and is found 

 occasionally with leaves entire. 

 Like A. artemisiaefolia it is com- 

 ing in from the Mississippi valley 

 along the railways and is found 

 principally in waste land about 

 the stations, but in low situa- 

 tions is spreading to adjacent 

 fields and gardens. Extends as 

 far west as Havre and Savoy on 

 the Great Northern and to Boze- 

 raan on the Northern Pacific. In- 

 frequent except eastward. Seeds 

 disseminated by water and in 

 mud. [Fig. 2.] 



11. ANTHEMIS COTULA. DC. 



Dog Fexxel; Mayweed. 



An annual ill-scented weed 

 about a foot high, with a level- 

 topped mass of white-rayed 

 flowers; leaves alternate and fine- 

 ly divided. Not infrequent in waste places in nearly every part of 

 the state and shows some disposition to spread and become troub- 

 lesome as it does in the more humid climate of the eastern states. 



Fiif. 2. Ambrosia tritid; 



12. "ARCTIUM LAPPA, L. Burdock. 



A coarse biennial about three feet high, with large leaves and 

 purple flowered heads disposed in a many-branched terminal panicle 

 each surrounded with a bur-like involucre. A European introduc- 

 tion common in the eastern states, but noted here only at Libby. 

 Thompson Falls, Plains and Big Timber, along roadsides and 



