210 DICOTYLEDONOUS PLANTS. 



5. A. artemisi/olia Linn. : leaves bipinnatifid, hoary underneath, the 

 uppermost pinnatifid ; racemes by threes, terminal ; branches fastigi- 

 ate. A. absynthifolia Mich. 



HAB. Fields. Penn. to Car. W. to Miss. Aug., Sept. . 

 Stem 4 6 feet high. Leares opposite below, alternate above. 

 Racemes loosely paniculate. Spines of the fruit very short. 



6. A. paniculata Mich. : stem branching, paniculate at the summit, 

 and with the petioles villous ; leaves green on both sides, bipinnatifid, 

 the segments lanceolate ; fruit somewhat clustered, small, obovate, 

 slightly awned. lea monophylla Walt. 



HAB. Old fields. Can. to Flor. July Sept. . Pursh. 

 Stem % 4 feet high. Flowers in simple terminal and axillary 

 racemes. 



7. A. hcterophyUa Muhl : stem paniculate ; cauline leaves pinnati- 

 fid, subdentate, petiolate, those of the branches lanceolate, sessile : pe- 

 tioles with long cilise ; racemes terminal, solitary. A.pervciana, Willd. 



HAB. Banks of streams. Penn. July Sept. Q}. Muhl. 



48. XANTHIUM. Lmn. 



Monoecious. STERILE PL. Involucre imbricate. Anthers 

 approximate, but not united. Receptacle chaffy. FERTILE 

 FL. Involucre 2-leaved, 1 -flowered. Carol none. Drupe 

 dry, muricato, 2-cleft. Nut 2-celled. 



Monoecia. Pentandria. 



1. X. stmmarium Linn. : stem unarmed, branching ; leaves cordate, 

 lobed, serrate, scabrous, 3-nerved; fruit elliptic, pubescent, armed 

 with rigid hooked bristles. 



HAB. Road sides. N. Y. to Car. W. to Miss. Aug., Sept. 

 0. Stew, 3 6 feet high. Flowers in axillary racemes. 



Clot-weed. 



2. X. macrocarpon De Cand. : stem unarmed, spotted ; leaves cor- 

 dute, lobed, obscurely sinuate-toothed, scabrous, 3-nerved ; fruit oval, 

 densely armed with short rigid uncinate bristles ; horns incurved. - 

 X. orientate Linn. X. maculatum Raf. 



HAB. Near salt water. N. S. Aug. $. Stem purple, spotted. 

 Fruit very large, woolly. 



3. X. spinosum Linn. : spines ternate ; leaves 3-lobed. 



HAB. Waste ground. Md, to Geor. Q.Stem 3 feet high. 

 Flowers small. Prkkly Clot-weed. 



SUBORDER VIII. ANTHEM IDE^. 

 49. SPARGANOPHORUS. Mich. 



Involucre somewhat globose, imbricate, with the scales re- 

 curved at the point. Receptacle naked. Acines crowned 

 with a small cartilaginous cup. Syngenesia. JEqualis* 



