POLYGONACEAE. Vol. I. 



12. Polygonum triangulum Bicknell. Missouri 

 Knotweed. Fig. 1626. 



Annual, bright green or somewhat yellowish-tinged, 

 similar to P. ramosissimum in habit, but smaller, stem 

 rather sparingly branched, usually 2°-4° tall. Leaves 

 mostly oblong or elliptic or slightly broadened up- 

 ward, 4"-i4" long, acute, rather persistent; ocreae 

 becoming very much lacerate; flowers sparingly clus- 

 tered, short-pedicelled; sepals mostly 5, yellowish- 

 margined, ¥'-¥' long ; stamens mostly 5 ; achene 

 3-angled, acute, about 1" long, broadly ovoid. 



Common near Atherton, Missouri. Aug.-Sept. 



13. Polygonum tenue Michx. Slender 

 Knotweed. Fig. 1627. 



Polygonum tenue Michx. Fl. Bor. Am. 1 : 238. 1803. 



Annual, glabrous, somewhat rough about the 

 nodes, stem very slender or filiform, erect, simple 

 or branched, somewhat 4-angled, 4'-i2' tall. Leaves 

 linear or linear-lanceolate, sessile, acuminate at the 

 apex, 2"-i2" long, articulated to the ocreae, i-ribbed 

 with a lateral impression on each side of the rib, the 

 margins minutely scabrous or serrulate ; ocreae fun- 

 nelform, soon lacerate; flowers several in the axil- 

 lary clusters, green, subsessile; sepals whitish; sta- 

 mens 8; fruit erect; achene 3-angled, black, i"-ii" 

 long, reticulated on the angles, the centre of its 

 faces smooth. 



Dry soil, Ontario to Minnesota, Nebraska, Georgia and 

 Arkansas. July-Sept. 



14. Polygonum Douglasii Greene. Doug- 

 las' Knotweed. Fig. 1628. 



Polygonum Douglasii Greene, Bull. Cal. Acad. (II.) 

 1 : 125. 1885. 



Annual, similar to the preceding species, gla- 

 brous, somewhat rough at the nodes, sometimes 

 slightly glaucous, stem erect, 8'-i8' tall, simple 

 or usually much branched, almost terete. Leaves 

 oblong or narrowly lanceolate, ¥-2' long, sub- 

 sessile, rather thin, flat or revolute, with no 

 lateral impressions parallel to the midrib; ocreae 

 oblique, short, soon lacerate; clusters axillary, 

 several-flowered; the flowers and fruit deflexed; 

 sepals green with white or rose-colored margins; 

 stamens 8; achene 3-angled, ii"-2" long, oblong 

 or ovoid-oblong, black, smooth and shining. 



Northwest Territory and British Columbia to New 

 Mexico, Nebraska and Oklahoma, east through On- 

 tario and New York to Vermont. June-Sept. 



6. TOVARA Adans. Fam. PI. 2 : 276. 1763. 



Annual or perennial herbaceous plants, becoming somewhat woody below. Stem mostly 

 erect, virgate, simple or virgately branched. Leaves alternate, _ membranous, acute at both 

 ends, continuous with the ocreae. Ocreae cylindric, fringed with bristles. Flower-clusters 

 not dense, remote. Racemes linear, very long and wand-like, conspicuously interrupted. 



