Obdeb 102.— KNOTWEEDS. 277 



a Calyx unequally 4-oleft. 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. . . .u 



o Flowers in leafless, terminal, spike-like racemes. . . .d 



c Flowers axillary, or rarely forming a leafy raceme f 



d Eaoeme one, dense. Stems decumbent at base 18, 14 



d Kaoemes several. Sheaths naked, not fringed 11, 12 



d Eacemes several. Sheaths bristly fringe-ciliate e 



e Style 2 (or 3)-oleft. Aohenia flat or lens-shaped 8-10 



e Style S-oleft. Aohenia sharply 8-cornered. Wet.... 5-7 



f Achenium protruding beyond the calyx, 3-angIed 3, 4 



1 Achenium included in the calyx, 8-angled 1,2 



1 P. avicnla're. £ird K. 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 lanoe-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, 2-3f. high. Leaves 

 lanoe-oblong or linear._ Aohenia smooth, dull. "W. 

 5 P. hirsu'tum. Hairy K. Hairy-tawny. Leaves lanceolate from a blunt base. S. 

 S 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. Oar'eyi.' Carey's K. Plant hairy. Spikes nodding, on very long stalks. 

 10 P. Persica'ria. Lady'-s-tlmmb. 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, c. 



12 P. incama'tum. Flesh-^ed, K. Spikes linear, nodding, the stalks and branches 



glandular-dotted. W. S. 



13 P. amphib'inm. Water K. Stem ascending from a prostrate, rooting base. 



Leaves lance-oblong. _Stamens 5. Spikes la^rge, dense, rose-red. 



14 P. vivip'aram. AVpine Bistort. Creeping at base. Lvs. lance-linear. Mts. N. 

 15 P. orienta'le. Prince's FeatTier. ' Stem stout, tall, with large, drooping spikes, f 



16 P. Virgima'nnm. lA/p-fl. K. Leaves large. Kacemes slender, flowers remote. 



17 P. oonvol'vulus. Knot-Bindweed. Eoughish. Eacemes axillary. Fruit dull. 



18 P. cilmo'de. Bearded B. Sheaths with a hairy ring. Panicles axil, and terminal. 

 1-9 P, dnmito'rnm. Sedge B. Calyx with the 8 outer sepals acutely wing-keeled. 



, 20 P. sagitta'tum. Scratch-grass. Lvs. lanoe-sagittate. Stamens 8. Styles 3. 

 21 P. arifo'lium. Arum-ki. S. Lvs. pointed, with pointed lobes. Stam. 6. Sty. 2. 



