706 THE POLYGONUM FAMILY. 



in character, and sometimes 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 

 mealiness of the Goosefoot family. 



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

 Fruiting perianth of 4 segments, 2 inner ones enlarged . . 2. Oxyria. 

 Fruiting perianth of 5 nearly equal segments 3. Polygonum. 



The Rhubarbs of our gardeners and druggists are species of the 

 genus 'Rheum, belonging to the Polygonum family. 



I. DOCK. KUMEX. 



Herbs or shrubs, the British species all perennials, with a thick 

 rootstock, and erect, furrowed, annual stems ; the thin sheathing sti- 

 pules never fringed on the edge, but soon becoming torn or jagged. 

 Lower leaves stalked and often large. Flowers numerous, small, her- 

 baceous, though often turning red, usually pedicellate, in whorl-like 

 clusters, axillary or in terminal racemes, often branching 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, with fringed stigmas. 



A considerable genus, spread 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 obtuse auricles) . Flowers mostly hermaphrodite. 

 (Docks.) 

 Inner perianth-segments entire, or with one or two scarcely 

 perceptible teeth. 

 Segments broadly ovate, more or less cordate. Panicle 

 narrow and crowded when in fruit, 

 jtfo tubercle on any of the perianth-segments ... 1. Grainless D. 

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

 Segments ovate, not cordate. 



Tall water-plant. Lower leaves above a foot long. 

 Panicle erect. A tubercle on all three perianth-seg- 

 ments 4. Water D. 



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

 Panicle very spreading. Perianths small. 

 A tubercle on all three perianth-segments . . 5. Clustered D. 

 A tubercle on one segment only 6. Red-veined D. 



