368 BUCKWHEAT FAMILY. 



Embryo mostly on the outside of mealy albumen, the radicle 

 pointing to the apex of the fruit. Juice acid or acrid. 



* Calyx of 6 sepals often of two sorts ; styles 3. 



1. RHEUM. Sepals all similar, petal-like, withering-persistent underneath the 3-winged 



fruit. Stigmas capitate or wedge-shaped. Stamens 9. 



2. KUMEX. Sepals of 2 sorts ; the 3 outer ones herbaceous and at !ength spreading ; the 



alternate inner 3 larger, somewhat colored, enlarging after flowering, becoming veiny 

 and dry, often bearing a grain-like tubercle on the back, and convergent over the 

 3-angled akene. Stigmas a hairy tuft. Stamens 6. 



* * Calyx of 5, rarely 4, more or less petal-like similar sepals, erect after flowering. 



8. POLYGON UM. Flowers in racemes, spikes, or else in the axils of the leaves. Akene 

 either lenticular when there are 2 stigmas, or triangular when there are 3. Embryo 

 curved round one side of the albumen ; cotyledons narrow. Stamens 4-9. 



4. FAGOPYKUM. Differs from one section of Polygonum mainly in having an embryo 

 in the center of the albumen, which is divided into 2 parts by the very broad leaf-like 

 cotyledons. The triangular akene longer than the calyx. Stamens 8. 



5^ POLYGONELLA. Flowers on solitary jointed pedicels (nodding in fruit) in slender 

 pauicled racemes. Leaves jointed at the base. Embryo slender and nearly straight, 

 lying in one side of the albumen. Stamens 8. 



1. RHEUM, RHUBARB. (Greek, from fiha, the old Greek name of 

 rhubarb.) Only the following species common; .thers are sometimes 

 cult, for ornament. 



R. Rhap6nticum, Linn, (i.e., Pontic Eha or Rheum}. GARDEN R. or 

 PIE PLANT ; the large fleshy stalks of the ample rounded leaves, filled 

 with pleasantly acid juice, cooked in spring as a substitute for fruit ; 

 flowers white, 'in late spring, in tall panicles. Old World. 



2 RUMEX, DOCK, SORREL. (Old Latin name.) The three en- 

 larged sepals which cover the fruit are called valves. Flowers greenish, 

 in whorls on the branches, forming panicled racemes or interrupted 



1. DOCK. Herbage bitter ; flowers perfect or partly monoecious, in 

 summer. 



* In marshes; stem erect, stout; leaves lanceolate or lance-oblong, flat, 

 not wavy ; valves entire or obscurely wavy-toothed in the first species. ^ 



- Pedicels longer than the fruiting calyx. 



R. Britannica. Linn. GREAT WATER DOCK. Common N. ; 5-6 

 high ; leaves often l-2 long, the margins obscurely erose-crenulate ; 

 flowers nodding on slender pedicels which are about twice the length of 

 the fruiting calyx ; the valves round-ovate or almost orbicular, very obtuse 

 and obscurely cordate, thin, nely reticulated, nearly ' wide, each bear- 

 ing a grain. N. Eng. and N. J., W. 



R. verticillatus, Linn. SWAMP D. Common N. ; 3-5 high ; fruit- 

 bearing pedicels slender and club-shaped, abruptly reflexed, 3-4 times 

 longer than the calyx ; valves somewhat rhombic and with narrow blunt 

 apex, each bearing a very large grain ; leaves thickish, the lowest often 

 heart-shaped at base ; raceme long and nearly leafless, the whorls loose. 



-t- -- Pedicels shorter than the fruiting calyx. 



R. salicif&lius, Weinm. WHITE D. Salt marshes arid lake borders ; 

 l-3 high ; leaves narrowly or linear-lanceolate ; pedicels much shorter 



