368 BUCKWHEAT FAMILY. 



Embr3-o mostly on the outside of mealy albumen, the radicle 

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



» Calyx of r> sepals often of two sorts ; styles 3. 



1. EIIEUM. Sepals all .-iinilar, petal-like, withering-persistent uiiilerneath the 3-\vinge(l 



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



2. RUMEX. Sepals of 2 sorts ; the 3 outer ones herbaceous and at 'ength spreading ; the 



alternate inner 8 larger, somewhat colored, enlarging after flowering, bocoming veiny 

 and dry, often bearing a grain-lil<e tubercle on the bat-k, and convergent over the 

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

 # * Calyx of 5, rarely 4, more or less petallike similar sepals, erect after flowering. 



3. POLYGONUM. 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 jtedicels (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 liha, the old Greek name of 

 rhubail).) Only the foUowiiag species common; others are sometimes 

 cult, for ornament. 



R. Rhapdnticum, Linn, (i.e., Pontic liha or Ilheum). Garden R. or 

 Pie Plant ; the large tieshy stalks of the ample rounded leaves, filled 

 with pleasantly acid juice, cooked in spring as a sub.stitute 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 pauicled racemes or interrupted 

 spikes. 



§ L Dock. Herbage hitter; flowers perfect or partly moncecions, in 

 summer. 



* III marshes; stem erect, .'itout ; leaves lanceolate or lance-oblonr/, flat, 

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



-I- Pedicels longer than the fruiting calyx. 



R. Britannica, Linn. Great Water Dock. Common N. ; .5°-6° 

 high ; leaves often 1^-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, finely reticulated, nearly i' wide, each bear- 

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



R. verticillatus, Linu. 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. salicifdiius, Weinm. White D. Salt marshes and lake borders ; 

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



