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, i"-l" long; stamens mostly 5; achcne 

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



Common near Atherton, Missouri. Aug.-Sept. 



13. Polygonum tenue Michx. Slender 

 Knotweed. Fig. 1627. 



Polygonum tenue Michx. Fl. Bor. Am. i : 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"-ij" 

 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.) 

 i : 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, i'-2 r 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, \\"-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. 



