302 POLYGONACE^. 



*** Flowers in axillary or terminal spikes. 



6. P. punclatuvi Ell. : stem branched ; leaves lanceolate, with pellucid 

 punctures, scabrous on the margin and midrib ; stipules slightly hairy, 

 ciliate ; spikes few-flowered, filiform, at first cernuous ; perianth glandular- 

 punctate; stamens 6 — 8; styles 2 — 3. P. Hydropiper Mich. P. hydro- 

 piper oides Pursh. 



Inundated grounds. Can. to Car. Aug., Sept. (T). — Stem 1 — 2 feet high, 

 slender, sometimes decumbent. Flowers white, in one or two slender simple 

 spikes. Nut lenticular or triquetrous. Plant very acrid. Water Pepper. 



7. P. mite Pers. : stem erect or ascending ; leaves narrow-lanceolate, 

 acuminate, entire, somewhat hairy ; stipules hairy, with long cilise ; flowers 

 octandrous, in crowded spikes ; styles 3. P. hydropiper oides Mich. 



Ditches and ponds. Can. to Car. July — Sept. (J). — Stem 18 inches high. 

 Flowers purplish, in somewhat crowded spikes. Leaves not acrid. Nut trique- 

 trous, purplish-black. Bearded Knotweed. 



8. P. Virginianum Linn. : stem simple ; leaves ovate-lanceolate, acu- 

 minate ; spike terminal, slender, very long ; flowers remote, pentandrous ; 

 perianth unequally 4-parted ; styles 2. P. Bislorta Walt. 



Shady woods. Can. to Flor. W. to Miss, July, Aug. %..—Stem 2—4 feet 

 high, somewhat angular, hairy near the summit. Leaves large, with hairy 

 stipules. Flowers white or purplish, in a very long naked and somewhat vir- 

 gate spike. Virginian Knotweed. 



9. P. amphibium Linn. : stem nearly erect ; leaves petiolate, oblong- 

 lanceolate, sometimes cordate at base ; flowers in dense terminal spikes, 

 pentandrous ; styles 2. P. cocciTieum var. terrestre Pursh. 



var, aquaticum Linn. : stem spreading on the surface of water ; leaves 

 ovate-lanceolate, cordate ; spike cyUndric-oblong. P. Jluitans Eaton. P. 

 coccitieum Big. 



Borders of swamps and ponds. N. S. W. to Miss. July. %. — Stem 8 — 12 

 inches long. Flowers large, reddish, in an ovate spike. The var. has the stems 

 long and the leaves broad-cordate and floating ; but it passes into the former. 



Water Knotweed. 



10. P. Pennsylva7iicum Linn. : stem erect, with tumid joints ; leaves lan- 

 ceolate, slightly hairy, petioled ; stipules smooth and naked ; spikes ob- 

 long, crowded, on glandular-hispid peduncles; flowers mostly octandrous; 

 styles 2. 



Margins of ponds and ditches. N. Y. to Car. W. to Miss. July, Sept. 

 (1). — £tem 2 — 4 feet high, geniculate, branched above. Flowers large, reddish, 

 in numerous crowded spikes. Stamens often 6. Pennsylvanian Knotweed. 



11. P. Persicaria Linn. : stem erect; leaves lanceolate -j stipules trun- 

 cate, ciHate ; spikes dense, ovate-oblong, erect, on smooth peduncles ; flow- 

 ers hexandrous ; styles 2. P. lapathifoliuni Linn. 



Waste places. Can. to Car. July, Aug. 0. — Stem 12 — 18 inches high, 

 erect or decumbent, branched, smooth, often purplish. Leaves on short petioles, 

 the upper surface usually marked with a dark-colored spot. Flowers reddish, 

 in erect oblong terminal spikes. Ladies' Thumb. 



12. P. orientale Linn. : stem ereet, paniculately branched, hirsute ; 

 leaves very large, petioled, ovate, acuminate, minutely pubescent ; stipules 

 hairy, salverform ; spikes terminal, dense, nodding, on hairy peduncles ; 

 flowers heptandrous ; styles 2. 



