294 Class XIX. Order I. 



Syn. SERRATULA NOVEBORACEXSIS. L. 



A tall plant, bearing a multitude of dark purple flowers, 

 which turn nearly black in decay. Stem about four feet high, 

 furrowed, purplish, branching at top. Leaves peduncled, lan- 

 ceolate, finely serrate, acuminate, paler underneath. Flowers 

 terminating the stem and branches, in a compound, flat topped 

 corymb. Scales of the calyx ending in a fine, slender awn. 

 Found in moist situations. Semtember. Perennial, 



312. BIDENS. 



BIDENS FRONDOSA. L. Common Burr Marygold. 



Flowers discoid ; outer calyx six times as long as 



the flower, its leaves ciliate at base ; lower leaves 



pinnate, upper ones ternate, lanceolate, serrate. Willd. 



A frequent and troublesome weed in corn fields, especially 

 where the soil is moist. Stem smooth, three or four feet hi-h. 



' O 



Lower leaves five-pinnate, sometimes ternate, leafets lanceo- 

 late, serrate. Flowers terminal, erect, flosculous, surrounded 

 by a large, leafy involucrum or outer calyx. Florets small, 

 yellow. Seeds oblong, flat, tipt with two barbed awns, by 

 which they adhere to the clothes, and to the coats of animals. 

 August, September. Annual. 



BIDENS TRIPARTITA L. Trifid Burr Marygold. 



Flowers discoid ; outer calyx longer than the flow- 

 er : seeds with three awns ; leaves trifid. 



Stem two or three feet high, branching; leaves opposite, 

 mostly three parted with lanceolate, serrate segments; the lower 

 leaves frequently pinnatifid, the upper ones in the American 

 plant generally simple. Calyx short in comparison with the 

 preceding. Seeds resembling those of the last with commonly 

 a third short awn between the other two. Swamps and ditches. 

 August. Annual. 



BIDENS CRYSANTHEMOIDES. Mich. Large flowerd Bidens. 

 Flowers erect, radiate ; outer calyx waved, much 

 shorter than the ray ; leaves lanceolate, serrate, con- 

 nate. 



