412 rOLYtiOXACK.K. (buckwiikat kamii.y.) 



grceiiisli, curved ; styles at leiiRtli lionkcil at the ajicx. — Drv riih 8i)il. Au- 

 gust-Sept, ii — I'laut 2°-4" luL-li. Leaves 3'-5' luiiy, li'-2f wide. 

 Spike 6' -12' long. 



§ 5. K«'iiis<JCAri.i)N. — Floicers m h i mnnil rliislers: ailji-r A-^-jxtrted : sta- 

 mens 6 or 8: sd/lts 2-3 : achenium Itiiliculiir or 3-ani/l<'(l : cotif/edons accum- 

 lit-iii. — Shins ire<iL-,l>raiuhiii;/,iirmtd on the umjles, petioles, etc. with recurred 

 prickles. 



IS. P. arifolium, L. Leaves iiastate, aeuniiuale, ineinbraiiaccous, iiii- 

 iiutelv dultcd and l)air\-, loiiR pftioled, the lobes aeute ; peduncles ratlier short, 

 bri.stly ; Howers white, souiewhat spiked; stamens 6; styles 2; achenium 

 lenticular. — Kice lieliis and wet ])laces, South Carolina, aud northward. 

 Jnnc-Oct. ® — Stems 2° - 3° long. Leaves 3' -4' long. 



111. P. sagittatum, L. Leaves small, sagittate, acute, short-petioled, 

 smooth; ])tMlnii(Us elongated, smooth; flowers white, capitate ; stamens 8 ; 

 styles 3 ; achenium .3-angled. — Wet places. June- Oct. (l) — Stem l°-30 

 long. Leaves r-2' long. 



§ 6. TiM.VKiA. — Flowers in axillari/ clusters or racemes: cali/x (jreenish 

 tvliite, ^-jHirted, the outer lobes keeled or witujed on the hack : stamens 8: sti/les 

 3, veri/ short: achenium 3-an;)led : cotyledons accumhent. — Annuals, with 

 twiniuq stems and cordate leaves. 



17. P. Convolvulus, L. Stem roughish, when small erect; leaves 

 long-petioled, sagittate-cordate, acuminate ; sheaths naked ; flowers in axillary 

 clusters, or in long interru])ted leafless racemes; fruiting calyx ovate, closely 

 investing the dull hlack achenium, the outer lobes keeled. — Cultivated ground. 

 Introduced. July - Sept. — Stems 1° - 3° long. 



18. P. cilinode, Michx. Minutely pubescent ; leaves ovate, acuminate ; 

 sheaths bearded at the ba.se; flowers in loose simple axillary and panicled 

 racemes; fruiting calyx nearly including the smooth and shining achenium. 

 the outer lobes slightly keeled. — Dry rocks on the mountains of North Caro- 

 lina, and nurtiiward. July-Sept. — Stem 3°-9°long. 



19. P. dumetorura, L. Smooth; leaves ovate, acuminate, long-peti- 

 oled ; sheaths naked ; flowers in long axillary more or le.«s leafy racemes ; 

 fruiting calyx somewhat spatulate, emarginate, much longer than the smooth 

 and sliining nchenium, the outer lobes winged, and decurrent on tlie pedicel. 

 — Low margins of fields and thickets. June - Se])t. — Stem 6^ - 12" long. 



4. THYSANELLA, Gray. 



Flowers polygamous. Cal_\ x corolla-like, deeply 5-parted, un<'hanged in 

 fruit ; lol)es erect, unecpial ; the 2 outer ones cordate at the l)ase ; the inner 

 smaller, pectinate fimbriate. Stamens 8. Styles 3. Achenium ovate, 3 

 angled, nearly included in the })ersistent calyx. Cotyledons on the outside of 

 the albumen. — An erect smooth and branching annual, with long linear 

 acute leaves, truncate cylindrical sheaths, fringed with long bristles, and 

 white or rose-colored flowers in closely bracted spikes. 



I. T. fimbriata. Gray. (Polygonum fimljriatum, £■//.) — Dry jiine bar- 

 rens, Georgia aud Florida. Sept. - Oct. — Stem branching above, l°-2° 

 high. Leaves 1'- 2' long. 



