130 FLOBA OF PHILADELPHIA. 



3. Flowers in axillary clusters ; stems more or less wiry, not twining. 



Plant prostrate ; acliene invested by the calyx. 



Leaves mostly acute; style 3-partecl to below the middle. 



13. P. aviculare. 

 Leaves mostly obtuse; style 3-parted to the base. 



14. P. littorale. 

 Plants prostrate, achene protruding beyond the calyx. 



15. P. maritimum. 

 Plants erect or ascending, rather stout. 



Leaves oval, oblong, or obovate, persistent. 



16. P. ereetum. 

 Leaves narrowly lanceolate or linear-oblong, persistent. 



17. P. ramosissimum. 

 Plants strictly erect and very slender. 18. P. tenue. 



4. Flowers in axillary and terminal ckisters, racemes or panicled racemes; 



stems mostly twining. 

 Stems twining; herbaceous vines. 



Outer segments of the calyx unchanged or keeled in fruit. 

 Achene granular and dull, ocreae not bristly. 



19. P. Convolvulus. 

 Achene smooth and shining, ocreae bristly. 



20. P. eilinode. 

 Outer segments of the calyx conspicuously winged in fruit. 



Calyx wings not incised. 21. P. scandens. 



Calyx wings incised. 22. P. cristatum. 



Stems stout, erect, tall; outer calyx-segments winged in fruit. 



23. P. Zuccarinii. 



5. Flowers in capitate clusters or racemes; stems climbing by recurved 



prickles. 

 Leaves sagittate; achene 3-angled. 24. P. sagittatum. 



Leaves halberd-shaped; achene lenticular. 25. P. arifoUum. 



1. Polygonum amphibium L. M. p. 360. Ponds. Summer. 



Montgomery — Shannonville (Cr.). Lancaster — York Furnace (Cr.) 

 (He.) (Li.). Northampton— CP.). Dauphin Steelton (Wn.). 

 Himterdon— (C). 

 New Castle— Qherry Island, Holly Oak, Vandyke, etc. 



2. Polygonum emersum (Michx.) Britton. M. p. 360. Swamps and 



moist soil. Summer. 

 BucJcs — Sellersville (Fr.). Delaware — Tinieum, T. C. Palmer (Fu.). 

 Chester — (P.). Lancaster — (P.). Northampton — 'Easton, Porter (B.C.). 

 Gloucester — 'Re-pSi.u^o (He.). Mercer — Below Trenton (C). Hun- 

 terdon — Bulls Island (C). 



3. Polygonum incarnatum Ell. M. p. 360. Wet soil. Summer. 



Lancaster— (P.) . Northampton— {P.). Dauphin — (P.). 

 Camden — Banks of Delaware (C). 



4. Polygonum lapathifolium L. M. p. 361. Waste places. Summer, 



Philadelphia — Fairmount Park (Ja.). Montgomery — Shannonville 

 (Cr.). Z>eZot(;are— Lansdowne (Gi.). Chester— West Chester (P.). 

 Cape May— Anglesea (He.) (Li.) 



5. Polygonum Pennsylvanicum L. M. p. 361. Moist soil. Summer. 



6. Polygonum Persicaria L. Lady's Thumb. M. p. 361. Waste places. 



Summer. 



7. Polygonum Careyi Olney. M. p. 362. Marshes. Summer. 



Burlington— Vomher.tan (C), Brown Mills (He.) (Li.). Camden— 



