148 POLYGONACEiE. Polygonum. 



tt Stem prostrate or climbing (not twining) : leaves sagittate or hastate : flowers capitate or somewhat racemose. 



6. Polygonum sagittatum, Linn. Arroiv-leaved Tear-thumb. 



Stem flaccid, retrorsely aculeate, 4 -angled ; leaves sagittate, acute, on short petioles ; 

 stipules sheathing; flowers somewhat capitate, mostly octandrous ; achenium acuminate. — 

 Linn. sp. 1. p. 364 ; Michx. fl. 1. p. 241 ; Pursh, fl. I. p. 2T2, ; Ell. sk. \.p. 458 ; Bigel. 

 fl. Bost. p. 158 ; Torr. fl. \. p. 407 ; Bart.fl. N. Am. 3. t. 101 ; Meisn. I. c. p. 64 ; Beck, 

 hot. p. 302; Darlingt. fl. Cest. p. 251 ; Hook. fl. Bor.-Am. 2. p. 131. 



Annual. Stem 2-5 feet long, slender, prostrate or supported by other plants, acutely 

 4-angled ; the angles armed with sharp reflexed prickles. Leaves 1—2 inches long and 

 6-8 lines wide ; the midrib and petiole prickly. Ochreas membranaceous, semicylindrical 

 or sheathing, smooth. J lowers in small terminal pedunculate heads ; the peduncles smooth, 

 rose-color or nearly white. Achenium nearly as broad as long, smooth, nearly black when 

 ripe. 



Wet thickets ; common. July - September. 



7. Polygonum arifolium, Linn. Halberd-leaved Tear-thumb. 



Stem flaccid, angular and sulcate ; leaves hastate, acuminate, on long petioles ; stipules 

 sheathing ; flowers somewhat racemose, distinct, hexandrous ; styles 2 ; achenium ovoid, 

 somewhat compressed. — Linn. sp. 1. p. 364 ; Michx. fl. I. p. 241 ; Pursh, fl. 1. p. 272 ; 

 Ell. sk. 1. p. 459 ; Bigel. fl. Bost. p. 158 ; Bart. fl. N. Am. 3. t. 100 ; Torr.fl. 1. p. 407 ; 

 Meisn. I. c. p. 65 ; Beck, hot. p. 251 ; Darlingt. fl. Cest. p. 251. 



Annual. Stem 3-6 feet long, supported by other plants, purplish red ; the angles armed 

 with prickles, which are more remote than in the preceding species. Leaves 2 — 5 inches 

 long, triangular in their outline ; the lobes at the base very acute, slightly hairy above, minutely 

 papillose underneath ; the petiole prickly. Racemes very few-flowered ; the flowers distinct 

 and finally rather remote, rose-color or nearly white : peduncles glandularly hispid. Cal)rx 

 rarely expanding. Styles 2, short, united at the base : stigmas capitate. Achenium large, 

 doubly convex, smooth. Cotyledons accumbent, oval. 



Low swampy grounds. August - September. This species does not agree with the 

 characters of the section in which it is placed by Meisner. 



§ 2. Embryo more or less horny. 



**** PERiiCARiA, Tourn. Flowers 4 - 8-androvs : styles 9 - 3 : achenium compressed or triangular, covered by the calyx : 

 colyledons accumbent, narrow. — Flowers in spikes or heads. 



8. Polygonum amphibium, Linn. Water Persicaria. 



Leaves elliptical or oblong -lanceolate, acuminate or rather obtuse, acute or somewhat 

 cordate at the base ; spikes dense, cylindrical or ovate ; flowers pentandrous ; styles two ; 



