s¥tf genesi a NECESsARtA. Ambrosia. 
On the banks of ponds and ditches : Pensyivania and 
Virginia. O. July- — Sept. v. v. The flowers of 
this genus are very inconspicuous. 
2. A. hirsutissima ; foliis arcte sessilibus simplicibus oblon- 
gis supra basin latescentem utrinque unidentatis, fruc- 
tu tetragono infra apicem quadrispinoso. Mich. Jl. 
amer. 2. p. 182. 
In the western parts of the Allegany mountains ©. 
July — Sept. v. v, 
3. A. hirsuta, aspera ; foliis 3 -lobis serratis, lobis ovali-lan- 
ceolatis acuminatis, fructu infra apicem 0-spinoso.— 
IVilld. sp. pl. 4. p. 375. 
Teon. Moris, hist. 3. s. Q. t. 1./. 4. 
On the banks of rivers and ditches : Pensyivania to Ca- 
rolina. 0. Aug. Sept. v. v. From five to eight 
feet high. 
4. A. foliis bipinnatifidis glabriusculis, petiolis longe cilia- 
tis, racemis terminalibus paniculatis, caule virgato. 
Willd. sp. pl. 4. p. 3/6. 
In old fields : Canada to Carolina. 0* June — Aug. v.v. 
5. A. foliis bipinnatifidis subtus canescentibus summis pin- 
natifidis, racemis terras terminalibus, ramis fastigiatis. 
IVilld. sp. pl. 4. p. ‘S76, 
In fields and waste grounds : Pensyivania to Carolina. 
0 . Aug. Sept. v. v. 
6. A. foliis glabris bipinnatifidis summis pinnatifidis, race- 
mis termina' ibus solitariis, ramis fastigiatis. IVilld. sp. 
pl. 4. p. 3 76. 
Teon. Pink. aim. t. 10. f. 5. 
In old fields and on road sides : Canada to Florida. 0. 
July — Sept. v.v. 
7. A. foliis caulinis pinnatifidis subdentatis petiolatis, rameis 
summis lanceolatis sessilibus, petiolis longe ciliatis, 
racemis terminalibus solitariis, caule paniculato. 
W illd. sp. pl, 4. p. 378. 
On the banks of rivers and ditches : near Philadelphia. 
0. July— Sept. v.v. 
667. XANTHIUM. Gen. pl. 142 6. 
i . X. caule inermi ramoso, foliis cordatis lobatis serratis 
scabris basi trinervibus, fructibus ellipticis pubescenti- 
bus setis rigidis uncinatis. — IVilld . sp. pl. 4. p . 373» 
m 
lidentala . 
trifida . 
elatior. 
artemisifolia. 
paniculata . 
he tero phy lia* 
Strumarium . 
