POPULAR FLORA. 193 



Calyx of B (rarely 4) nearly similar sepals, all more or less petal-like. 



Stamens 4 to 9 ; akene generally smiiU ; cotyledons narrow, {Polygannm) Knotweed. 



Stamens 8; styles 3: akene triangular, shaped like a beechnut, much longer than the 

 calyx : cotyledons very broad and folded in the inealy albumen : root annual : 

 leaves nearly halberd-shaped : flowers white, corymbed, (Fagoptjrum) *Buckwheat. 



Calyx of 6 sepals, and 



All ahke and petal-like (White): stamens 9: styles 3, (Rheum) *Eiiubakb. 



Three outer ones herbaceous and spreading: three inner larger, especially after flow- 

 ering, ivhen they close over tLe triangular akene: flowers dicecious: leaves 

 sour, eared or halberd-shaped, {Rumex, § Acttosella) Sorkel. 



Flowers perfect or polygamous : leaves bitter: coarse herbs, (Rumex) Dock. 



Knot weed. Polygonum. 



* Flowers single or several together in the axils of the loaves, greenish or whitish: sheaths (stipules) 



cut-fringed or torn into narrow shreds. 



1. Common Knotweed, Knotgrass, or Goosegiiass. Spreading on the ground, small ; leaves 



sessile, lance-shaped or oblong, pale; a variety has nearly upright stems and oblong or oval leaves. 

 The commonest weed in yards and waste places. P. aviculdre. 



2. Slender K. Upright, somewhat branched; leaves linear, acute, sheaths fringed. Dry soil. P.tenue, 



* * Flowers in terminal hoads, spikes, or racemes. 

 1- Not twining nor climbing, and leaves not heart-shaped nor arrow-shaped: calyx petal-like and 



5-parted, except in No. 10. 



3. Oriental K. or Prince's Feather. Tall annual, 4° to 7° high; leaves ovate; spikes of rose- 



colored flowers long and nodding; stamens 7; akene flattish. Gardens. P. orientale. 



4. Water K. Stems floating in water, or rooting in mud, or upright; leaves lance-shaped or oblong; 



spike thick and short ; flowers rose-red ; stamens 5 ; styles 2. P. amphibium. 



5. I'ennsylvania K. Stem upright, 1° to 3° high; leaves lance-shaped; spike oblong, thick, erect, 



its peduncle beset with club-shaped bristles or glands; flowers rose-colored; stamens 8; akene 

 flat. Moist ground. P- Penmyhdnicum. 



6. Lady's-Thumb K. Stem«, &;c. like the last and next, but no bristles on the peduncle; leaves with 



a darker spot on the upper side; spike short and thick, erect; flowers greenish-purple; stamens 

 6. Very common in waste places. P, Persicaria. 



7. Smaetweed or Water-Pepper K. Upright, annual, 1° or 2° high, very acrid and biting to the 



taste; leaves and also the greenish sepals marked with fine transparent dots; spikes short but 

 loose, drooping; akene flattish or bluntly triangular. Moist ground, common in waste places, 

 yards, and near dwellings. P. IlydrojAper. 



8. Wild Smartweed K. Upright, 1° to 3° high from a perennial root, biting like the last, and the 



leaves dotted; spikes very slender, erect, whitish or flesh-color; stamens 8; styles 3; akene sharply 

 triangular. Wet places. P. acre. 



9. Mild Water-Pepper K. Upright, 1° to 3° high; often creeping at the base and rooting in water; 



leaves roughish, not biting, narrowly lance-shaped ; spikes slender, erect, rose-color; stamens 8; 

 style 3-oleft at the top ; akene sharply triangular. Shallow water. P. hyclropiperoides. 



10. Virginia K. Stem 2° to 4° high, angled; leaves large, ovate or lance-ovate, taper-pointed j flow- 



