sYNGENEsiA NECESSARIA. Ambrosia. 
581 
On the banks of ponds and ditches : Pensylvania and 
Virginia, 0. 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. Midi. Jl. 
amer. 2. p. 182. 
In the western parts of the Allegany mountains 0. 
July — Sept. V. V. 
3. A. hirsuta, aspera ; foliis 3 -lobis serratis, lobis ovali-lan- 
ceolatis acuminatis, fructu infra apicem 6-spinoso. — 
IVilld. sp. pl. 4. p. Zy 5. 
Teon. Moris, hist. 3. s. 6. t. l.f.A. 
On the banks of rivers and ditches : Pensylvania to Ca- 
rolina. O. Aug. Sept. V. V. From five to eight 
feet high. 
4. A. foliis bipinnatifidis glabriusculis, petiolis longe cilia- 
tis, racemis terminalibus paniculatis, caule virgato. 
IVilld. sp. pl. 4. p. 376 . 
In old fields : Canada to Carolina. O. June — Aug. v.v. 
5. A. foliis bipinnatifidis subtus canescentibus summis pin- 
natifidis, racemis ternis terminalibus, ramis fastigiatis. 
IVilld. sp. pl. 4. p. 376 . 
In fields and waste grounds : Pensylvania to Carolina. 
O . Aug. Sept. 7;. 7;. 
6. A. foliis glabris bipinnatifidis summis pinnatifidis, race- 
mis terminalibus solitariis, ramis fastigiatis. IVilld. sp. 
pl 4. p. 376 . 
Teon, Pluk. aim. i. 10. f. 5. 
In old fields and on road sides : Canada to Florida. 0 . 
July — Sept. V. V. 
7 . A. foliis caulinis pinnatifidis subdentatispetiolatis, rameis 
summis lanceolatis sessilibus, petiolis longe ciliatis, 
racemis terminalibus solitariis, caule paniculato. 
IV illd. sp. pl. 4. p. 37 s. 
On the banks of rivers and ditches : near Philadelphia. 
O. July — Sept. v.v. 
667 . XANTHIUM. Gen. pl 1426. 
l, X. caule inermi ramoso, foliis cordatis lobatis serratis 
scabris basi trinervibus, fructibus ellipticis pubescenti- 
bus setis rigidis uncinatis. — IVilld. sp. pl 4. p. 3/3. 
lidentata. 
trifida. 
elatior. 
artemisifolia. 
paniculata. 
heterophylla. 
Strumarlum. 
