SPECIES AND VARIETIES. 261 



d uncles ; involucral bracts broadly scarious ; florets of the ray 

 and disk yellow. — Corn Marigold. — A cornfield weed. Fl. 

 June to August. 



(148) Matricaria. Wild Chamomile. • 

 M. Chamomilla: annual, closely resembling Anthemis 

 Cotula ; stems erect, branching ; leaves bipinnatifid, with short 

 narrow linear segments; flower-heads rather large, on ter- 

 minal peduncles, the involucral bracts nearly all of the same 

 length, with scarious edges ; ray-florets white ; receptacle much 

 elongated as the flowering advances, scaly between the florets ; 

 achenes without any border. — Fields and waste places. Fl. 

 June, July. 



(149) Bidens. 



B. cernua : annual ; stems erect, 1-2 feet high, with spread- 

 ing branches ; leaves sessile, lanceolate, serrated ; flower-heads 

 drooping, on terminal peduncles, the florets yellow, usually all 

 tubular, but occasionally a few of the outer ones become ligu- 

 late ; awns of the achenes usually 2—3, rarely 4. — Bur Mari- 

 gold. — Wet ditches and marshes. Fl. July to September. 



B. tripartita difiers chiefly in the leaves being stalked, 

 and deeply cut into 3-5 lanceolate segments, in the flower- 

 heads being rather less drooping, and in the achenes usually 

 having only two awns or bristles. 



(150) Eupatorium. 



E. cannabinum : stems erect, 3-4 feet high ; leaves divided 

 into three broadly lanceolate, coarsely-toothed lobes, slightly 

 downy ; flower-heads numerous, in compact terminal corymbs, 

 pale reddish-purple ; involucres cylindrical, of few unequal 

 bracts, usually containing five florets. — Hemp Agrimony. — - 

 Banks and moist bushy places. Fl. July, August. 



