8YNGENESIA NficEssARiA. Ambrosla. 



511 



On the banks of ponds and ditches : Pensylvania and 

 Virginia. O. Ji^'ly — Sept. v. v. The flowers of 

 this genus are very inconspicuous. 



2. A. hirsotissima ; foliis arete sessiUbus simplicibus oblon- lidentala. 



gis supra basin laiescentem utrinque unidentatis, fruc- 

 tu tetragoDo intra apicem quadrispinoso. Mich. fi. 

 amer. 2. p. 182. 

 In the western parts of the Allegany mountains Q. 

 July — Sept. V. V. 



3. A. hirsuta, aspera ; foliis 3 -lobis serratis, lobis ovali-lan- trifida. 



ceolatis acuminatis, fructu infra apicem 6-spinoso. — 

 IViltd. sp. pi. 4. p. 375. 



Icon. Moiis. hist. 3, s. 6. t. l.f.4. 



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 bipinnatifijis glabriusculis, petiolis longe cilia- elatior, 



tis, racemis terminalibus paniculatis, caule virgato. 

 lFUId.sp.pl. 4. p. 3/6. 

 In old fields : Canada to Carolina. ©. June — Aug. v. v. 



5. A. foliis bipinnatifidis subtus canescentibus summis pin- artemislfolia. 



natifidis, racemis ternis terminalibus, ramis fastigiatis, 



IFilld. sp. pi. 4. p. 3/6. 

 In fields and waste grounds : Pensylvania to Carolina. 



O- Aug. Sept. V. V. 

 5. A. foliis glabris bipinnatifidis summis pinnatifidis^ race- paniculata. 



mis termina'ibus solitariis^ ramis fastigiatis. IVilld. sp. 



pi. 4. p. 376. 

 Icon. Ph/k. alm.t. 10./. 5. 

 in old fields and on road sides : Canada to Florida. ©. 



July — rfept. V. V. 



7. A. foliis caulinis pinnatifidissubdentatispetiolatis, rameis heterophylla. 

 summis lanceolaiis sessilibus, petiolis longe ciliatis, 

 racemis terminalibus solitariis, caule paniculato. 

 iV illd. sp. pi. 4. p. 37s. 

 On the banks of rivers and ditches : near Philadelphia. 

 O. July — Sept. v.v. 



667. XANTHIUM. Gen. pi. 1426. 



1. X. caule inermi ramoso, foliis cordatis lobatis serratis Strumarium. 

 scabris basi trinervibus, fructibus ellipticis pubescenti- 

 bus setis rigidis uncinatis. — IVilld. sp. pi. 4. p. 373. 



