POLYGONACEAE 



77 



1. F. esculentum Moenoh. Buckwheat. 1°-2° high, smootbish: 

 flowers whitish: achene smooth. — Occasionally ocjours along railroads and 

 in waste places. Jnlj-August. 



3. POLYGONUM L. 

 Herbs prostrate, erect or twining. Leaves oontinnous with or jointed 

 to the stipules (ochreae). Calyx 4-5-parted. Stamens 5-9. Styles 2-3- 

 parlied or cleft. Fruit a lenticular or triangular achene. Probably includes 

 several distinct genera. 



Plants not twining. 



Flowers in terminal racemes. I. Smartweed. 



Lower flowers, at least, in axillary clusters. II. Knotweed. 



Plants twining. III. 



Calyx 5-parted. 



Ochreae not bristle-bearing. 

 Perennials. 

 Annuals. 



Peduncles almost smooth. 

 Peduncles very glandular. 



Style-branches barely exserted. 

 Style- branches long-exserted. 

 Ochreae bristle bearing. 



Racemes thicli ; not interrupted. 

 Plant glabrous to puberuleut. 

 Plant hispid. 

 Racemes slender ; usually interrupted. 

 Ochreae strigose. 

 Ochreae smooth. 



Racemes usually drooping. 

 Racemes erect. 

 Calyx 4-parted. 



II. 



1. P. emermm. 



2. P. lapathifoKum. 



3. P. Pennsylvanieum. 



4. P. longislylujn. 



5. P. Persicaria. 

 9. P. orientate. 



6. P. hydropiperoides. 



P. Hydropiper. 

 P. punctatum. 



10. P. Virginianum. 



11. P. aviculare. 



Plants prostrate. 



Plants erect or ascending. 



Leaves oblong or oval . 12. P. erecium. 



Leaves lanceolate to linear. 



Achene twice the length of the calyx. 13. P. exsertum. 



Achene enclosed, or nearly so, by calyx. 



1 ° or more high. 14. P. ramossissimum. 



1° or less high. 15. P. tenue. 



III. 

 Stems not prickly. 



Calyx not wing-margined in fruit. 16. P. Convolvulus. 



Calyx strongly wing-margined in fruit. 17. P. scandens. 



Stems prickly. 18. P. aagUtaium. 



1. P. emersum (Michx.) Britton. l°-3° high, usually hairy : leaves 

 ovate-lanceolate : spikes 1-2, I'-S' long : flowers bright rose color. — 

 Common in swampy ground. 



2. P. lapatbifoUum L. l°-3° high, smooth : leaves lanceolate, 2'-5'' 

 long : spikes erect, l'-2'' long : flowers white or pink : stamens 6. — Infre- 

 quently occurs in waste places. 



