ORDER 102—KNOTWEEDS. QTT 
a Calyx unequally 4-cleft. Styles 2, long, deflexed....16 
a Calyx equally 5-parted. Styles erect....b 
b Sheaths with a spreading border. Stamens 7. Plant tall....15 
b Sheaths not bordered. Stamens 5, 6, or 8....¢ 
= Flowers in leafless, terminal, spike-like racemes....d 
= Flowers axillary, or rarely forming a leafy raceme....f 
d Raceme one, dense. Stems decumbent at base....18, 14 
d Racemes several, Sheaths naked, not fringed....11, 12 
d Racemes several. Sheaths bristly fringe-ciliate. ..¢ 
e Style 2 (or 3)-cleft. Achenia flat or lens-shaped....8-10 
e Style 8-cleft. Achenia sharply 8-cornered. Wet.. 5-7 
f Achenium protruding beyond the calyx, Hangled. 28,4 
f Achenium included in the calyx, 8-angled....1, 2 
1 P.avicula’re. Bird HK. Prostrate or erect. Leaves elliptic-lanceolate, acutish at 
each end. Achenia striate, dull. Very common. 
2 P.ten’ue. Slender K. Slender, rigidly erect. Leaves lance-linear, erect, acute. 
8 P. marit/imum. Sea K. Prostrate, diffuse, glaucous, close-jointed. Leaves 
linear-oblong, fleshy. Achenia smooth, shining. E. 
4 P, ramosis’simum. Lake K. Erect, much branched, 2-8f. high. Leaves 
lance-oblong or linear, Achenia smooth, dull, W. 
5 P.hirsu’tum. Hairy K. Hairy-tawny. Leaves lanceolate from a blunt base. 8. 
6 P. hydropiperoi’des. Mild Water-pepper. Stem smooth. Leaves linear-lanceolate, 
not acrid, tapering at both ends. Spikes slender. Calyx dotless. 
7 P.aere. Sharp W. Stem smooth. Leaves biting, dotted as well as the calyx, 
lanceolate, pointed. Spikes very slender, thread-form. 
8 P. hydropi’per. Water-pepper. Smooth. Leaves very biting, dotted. Spikes 
short, nodding. Calyx dotted. Achenia roughened. 
9 P.Car’eyi. Carey's K. Plant hairy. Spikes nodding, on very long stalks. 
10 P. Persica’ria. Lady’s-thumb. Leaves marked with a brown spot. Spikes 
short, dense, erect. Achenia shining, flattened. 
11 P. Pennsylvan’/icum. Pennsylvania K. Spikes oblong, dense, with glandular- 
hispid stalks and pedicels. Achenia with flat sides. ¢. 
12 P.incarna/tum. Flesh-red K. Spikes linear, nodding, the stalks and branches 
glandular-dotted. W. 8. 
18 P. amphib’ium. Water K. Stem ascending from a pisatiats, rooting base. 
Leaves lance-oblong. Stamens 5. Spikes large, dense, rose-red. 
14 P. vivip’arum. Alpine Bistort. Creeping at base. Lvs, lance-linear. Mts. N. 
15 P. orienta/le. Princes Feather. Stem stout, tall, with large, drooping spikes. + 
16 P. Virginia’num, Lip-jl. K. Leaves large. Racemes slender, flowers remote. 
17 P. convol’/vulus. Knot-Bindweed. Roughish. Racemes axillary. Fruit dull. 
18 P. cilino’de. Bearded B. Sheaths with a hairy ring. Panicles axil. and terminal. 
19 P.dumito’rum. Hedge B. Calyx with the 8 outer sepals acutely wing-keeled. 
20 P. sagitta’tum. Scratch-grass. Lvs. lauce-sagittate. Stamens 8. Styles 3. 
21 P. arifo/lium, Arum-lv. S. Lys. pointed, with pointed lobes. Stam. 6. Sty. 
