444 THE POLTGOSTUM EAMILT. 



styles or stigmas. Fruit a small, seed-like nut, enclosed in the 

 persistent perianth. Embryo of the seed straight or curved, in 

 a mealy albumen. 



A considerable Order, dispersed over every part of tlie globe, from tbe 

 hottest tropical plains to the extreme Arctic regions, or to the highest 

 mountain-summits, close to the limits of perpetual snows. Some tropical 

 species are tall, woody climbers, or erect shrubs, but the majority of the 

 Order are herbs approaching the Goosefoot family in character, and some- 

 times in habit, but always readily known by their sheathing stipules, even 

 when reduced to a narrow ring or a mere line surrounding the stem. They 

 also very seldom acquire any of the meaHness of the Goosefoot famUy. 



Fruiting perianth of 6 segments, 3 inner ones often enlarged . . 1. Dock. 



Pruiting perianth of 4 segments, 2 inner ones enlarged 2. Oxteia. 



Fruiting perianth of 5 nearly equal segments 3. Polygoktiii. 



The Shiibarbs of our gardeners and druggists are species of the genus 

 Rheum, belonging to the Polygonum family. 



I. DOCK. RTJMEX. 



Herbs or shrubs, the British species aU perennials, with a thick rootstock, 

 and erect, furrowed, annual stems ; the thin sheathing stipules never fringed 

 on the edge, but soon becoming torn or jagged. Lower leaves stalked and 

 often large. Flowers numerous, small, herbaceous, though often turning 

 red, usually pedicellate, in whorl-like clusters, axillary or in terminal 

 racemes, often brandling into panicles. Perianth deeply 6-cleft; when in 

 fruit the 3 inner segments become enlarged and close over the triangular 

 nut. Stamens 6. Styles 3, very short, witli fringed stigmas. 



A considerable genus, spi'ead over the greater part of the world, very 

 readily distinguished from the rest of the Order, but the species vary so 

 much in appearance that it is often very difficult to fix their real limits. 

 They can also seldom be determined without the fruiting perianth, from 

 which most of the characters are taken. They may be readily distributed 

 into two distinct sections, the true Docks and the Sorrels. 



leaves never hastate at the base (though often cordate, with ob- 

 tuse auricles). Flowers mostly hermaphrodite (Docks). 

 Inner perianth-aegments entire, or with one or two scarcely per- 

 ceptible teeth. 

 Segments broadly ovate, more or less cordate. Panicle narrow 

 " and crowded when in fruit. 



ITo tubercle on any of the perianth-segments 1 . Grainlesg D. 



A tubercle on one at least of the perianth-segments ... 2. Curled D. 

 Segments ovate, not cordate. 

 TaU water-plant. Lower leaves above a foot long. Panicle 



erect. A tubercle on all three perianth-segments . . 3. Great D, 

 Plant seldom above 3 feet. Lower leaves not a foot. Pani- 

 cle very spreading. Perianths small. 



A tubercle on all three perianth-segments 4. Sharp D. 



A tubercle on one segment only 5. Sed-veined D. 



Inner periattfh-segments toothed on the edge, one at least of the 

 teeth ending in a Jine point. 



Panicle erect. Pedicels longer than the perianth 6. Broad-leaved D, 



Panicle very spreading. Pedicels shorter than the fruiting 

 perianth, 

 leaves chiefly radical. Pedicels thickened. Teeth of the 



perianth-segments stiff and short 7. Fiddle D. 



Panicle leafy. Perianths densely clustered with long fine 



teeth to the segments 8. Golden D. 





