563 



BUCKWHEAT FAMILY. 



24. Polygonum Rayi Babingt. Ray's Knotweed. (Fig. i;, 



Polygonum Rayi Babingt. Man. Brit. Bot. Ed 2 

 275- 1848. 



Perennial or annual, glabrous, slightly glau- 

 cous, stem 3'-24' long, prostrate, usually much 

 branched, striate. Leaves ovate-lanceolate or 

 oblong, $"-15" long, short-petioled, acute or 

 obtusish at the apex, veined beneath, incon- 

 spicuously so above, shorter than the internodes, 

 inconspicuously jointed to the ocreae; ocreae 

 2-parted, becoming lacerate, silvery, brown and 

 glaucous at the base when old; flowers 2-4 to- 

 gether in the axils; stamens 5 or 6; style short, 

 3-parted to the base; achene ovoid, 3-angled, 

 2 //_y/ long, slightly granular but shining, much 

 exceeding the calyx. 



In waste places, New Brunswick and Prince Ed- 

 ward Island to British Columbia, south along the 

 Atlantic Coast to Virginia. Naturalized from 

 Europe ? May-Sept. 



25. Polygonum erictum L. Krix-t 

 Knotweed. (Fig. 1342.) 



Polygonum erectum L. Sp. PI. 565. 1753. 



Annual, glabrous, stem erect or ascending, y-a* 

 high, terete, nearly simple or much branched. 

 Leaves oval, oblong or obovate, suttseasile or 

 short-petioled, 3"-! 8" long, obtuse or subacute at 

 the apex, conspicuously jointed to the ocreae; 

 ocreae oblique, funnelform, soon lacerate, silvery 

 when young; flowers 1-2 together in the axils; 

 calyx greenish, enlarged in fruit; stamens 6 (some- 

 times 5) style very short, 3-parted to near the 

 base; achene ovoid -pyramidal, 3-angled, \W 

 long, reticulated and dull, invested by the calyx, 

 or the apex slightly protruding. 



In moist or dry soil, Ontario to the N"rthwr-t Ter- 

 ritory, Tennessee and Arkansas. July-Sept. 



26. Polygonum exsertum Small. Long 

 fruited Knotweed. (Fig. 1343.) 



P. cxserlum Small, Bull. Torr. Club, 21: 172. 1894. 



Annual, glabrous, sometimes slightly glaucous, 

 stem slender, brownish, erect or nearly so, con- 

 spicuously striate, branched, i / ^-3tall. Leaves 

 lanceolate, rarely oblanceolate, l /t'-\%' long, acute 

 or cuspidate at the apex, acuminate at the base, 

 nearly sessile; ocreae 2-4-parted when young, soon 

 lacerate, silvery, becoming brownish; calyx green- 

 ish, or white, 6-parted to near the base; stamens 5 

 or 6, included; style 3-cleft or 3-parted, very short; 

 achene 3-angled, narrowly pyramidal, 2#"-3" 

 long, more or less constricted above the middle, 

 chestnut-brown, smooth, shining, 2-3 times as long 

 as the calyx, at length twisted. 



Northwest Territory, south to Illinois. M> 

 and Nebraska and on the Atlantic coast, in brackish 

 marshes, from Maine to New York. Aug.-Oct. 



