236 POLYGONACEAE 



styles mostly 2, sometimes 3, usually partially united ; stigmas capitate. Achenes 

 mostly lenticular, sometimes 3-angular, usually black, smooth or granular. 

 Endosperm horny; cotyledons accumbent. 



Racemes terminal only and usually solitary; plants aquatic perennials. 

 Ocreae without spreading foliaceous tops. 



Plant usually floating, or decumbent and rooting; leaves of an oblong type, glabrous, 



acute or obtuse. 1. P. coccinea. 



Plant usually diffuse and emersed ; leaves of a lanceolate type, pubescent, acumin- 

 ate. 2. P. Muhlenbergii. 

 Ocreae with spreading foliaceous tops; leaf-blades narrowly oblong or lanceolate 

 (broader in floating forms), pubescent. 3. P. Hartwrightii. 

 Racemes axillary as well as terminal, numerous; annuals. 

 Ocreae without marginal bristles. 



Racemes erect; glands on the branches and inflorescence numerous, stalked. 



4. P. omissa. 

 Racemes dropping; glands on the branches and inflorescence sessile. 



Styles united only at the base. 5. P. incarnata. 



Styles united to about the middle. 



Leaves deep green on both sides. 6. P. lapathifolia. 



Leaves pale beneath. 7. P. incana. 



Ocreae bristle-fringed. 



Racemes oblong or cylindric, about 1 cm. thick in fruit; perianth not punctate, 



usually pink to red-purple. 8. P. Persicaria. 



Racemes slender, loosely flowered, about 5 mm. thick in fruit; perianth white 



or pale green, copiously punctate. 



Racemes erect; achenes smooth and shining. 9. P. punctata. 



Racemes nodding at least in fruit; achenes granular and dull. 



10. P. Hydropiper. 



1. P. coccinea (Muhl.) Greene. Perennial, glabrous, or the young shoots 

 somewhat pubescent; stem 5-50 dm. long; leaves oblong or elliptic, 3-10 cm. 

 long, glossy, obtuse or acute at both ends, or when growing in mud more elongate, 

 elliptic-lanceolate and acute; raceme spike-like, 1-3 cm. long; perianth light rose- 

 colored; achenes lenticular, black. Polygonum amphibium Hook., notL. Persi- 

 caria plattensis, P. subcoriacea, P. psychrophila, P. oregana, and P. laetevirens 

 Greene. In water or rarely in mud: Me. -N.J. N.M. Calif. -Alaska. 

 Plain Mont. Je-Au. 



2. P. Muhlenbergii (Meisn.) Small. Perennial, more or less strigose- 

 hispid throughout; stem erect or creeping at the base, 3-8 dm. high, simple; 

 leaf-blades broadly lanceolate, 5-20 cm. long, acuminate or acute; racemes spike- 

 like, linear or linear-oblong, 3-10 cm. long; perianth dark rose-colored, rarely 

 pink, 4 mm. long; achenes lenticular, black, granular but shining. Polygonum 

 Muhlenbergii (Meisn.) S. Wats. P. emersum (Michx.) Britton. Persicaria 

 emersa (Michx.) Small. P. propinqua and P. Wardii Greene. In swamps and 

 shallow water: Me. Va. N.M. Calif. B.C.;Mex. Plain Submont. Je-S. 



3. P. Hartwrightii (A. Gray) Greene. Perennial, more or less hispid 

 throughout; stem ascending or suberect, 3-7 dm. long, or rarely floating in water; 

 leaf -blades narrowly lanceolate or oblong-lanceolate or oblong, 6-18 cm. long; 

 raceme spike- like, oblong or ovoid, 1-3 cm. long, erect; perianth rose-colored, 

 3-4.5 cm. long; achenes lenticular, 2.5 mm. long, black, smooth and shining. 

 Polygonum Hartwrightii A. Gray. Persicaria muriculata and P. villosula Greene. 

 Wet places and shallow water. Me. Pa. Calif. Wash. Sask. Plain 

 Submont. Je-S. 



4. P. omissa Greene. Annual; stem 3-6 dm. high, with copious stipitate 

 glands; ocreae short, cup-shaped; leaf -blades 5-10 cm. long, lanceolate or oblong- 

 lanceolate, glabrous, punctate; racemes short-oblong or ellipsoid, 1-2 cm. long; 

 perianth deep pink, about 4 mm. long; achenes round-ovate, black and shining, 

 nearly flat on one side. Polygonum omissum Greene. Wet ground and dried- 

 up ponds: Kans. Colo. Plain. Jl-S. 



5. P. incarnata (Ell.) Small. Annual, nearly glabrous throughout; stem 

 erect, 6-10 dm. long, more or less thickened at the nodes; leaf -blades lanceolate 

 or linear-lanceolate, 5-20 cm. long, acuminate or acute; racemes linear, 3-8 cm. 

 long, drooping; perianth whitish, green, or rose-colored, 2-3 mm. long; achenes 

 lenticular, rarely 3-angled, dark brown or black, shining, smooth. Polygonum 

 incarnatum Ell. Wet places: Vt. Fla. Calif. Ida. Plain -Submont. Jl-O. 



