PLANTS OF SOUTHERN NEW JERSEY. 725 



[. Body of mature bur more than twice as long as thick. 



d. Beaks of bur straight or nearly so, prickles relatively few. 



Xanthium canadense, p. 726 

 dd. Beaks of bur incurved or hooked, prickles very numerous. 



X. commune, p. 726 

 cc. Body of mature bur thick-ovoid, not more than twice as long as 

 thick. X. echinatum, p. 726 



bb. Pistillate involucre not conspicuous or prominently spiny. 



c. Leaves palmately 3-5 lobed, or undivided, plant 10-50 dm. high. 



Ambrosia trifida, p. 725 

 cc. Leaves finely pinnatifid, plant 3-18 dm. high. 



Ambrosia artemisiifolia, p. 725 



IVA L. 



Iva oraria Bartlett. Marsh Elder. 



Iva oraria Bartlett, Rhodora 1906, 26. [Charles River, Boston]. 

 Iva frutescens Britton 142. — Keller and Brown 313. 



Common on the salt marshes of the coast, usually bordering 

 the ditches. 



This plant, resembling a big coarse Ragweed, borders the edges 

 of the tidal creeks and thoroughfares which intersect the salt 

 marshes in all directions. It is constantly associated with 

 Baccharis and Spartina strict a. 



Fl. — Early August to late September. 



Maritime. — Sandy Hook (NB), Long Branch, Forked River, Seaside 

 Park, Barnegat Pier, Surf City (L), Cedar Bonnet (L), Atlantic City, 

 Absecon, Ocean City (S), Piermont, Wildwood, Cape May, Dennisville (S). 



AMBROSIA L. 



Ambrosia trifida L. Great Ragweed. 



Ambrosia trifida Linnseus, Sp. PI. 987. 1753 [Virginia and Canada]. — Knies- 



kern 18. — Britton 143. 

 Ambrosia trifida in^grifolia Britton 143. 



Low moist, shady ground; frequent in the Northern and less 

 so in the Middle district, along streams. 

 Fl. — Late July to early September. 



Middle District.— New Egypt, Kaighns Pt., Springdale (S), Woodstown 

 (C), Salem (S). 



Ambrosia artemisiifolia L. Ragweed. 



Ambrosia artemisiifolia Linnseus, Sp. PL 987. 1753 [Virginia and Pennsyl- 

 vania]. — Knieskern 18. — Britton 143. 



