BUCKWHEAT FAMILY. 289 



P. Hydrdpiper, Common S. or Water Pepper. Low or wet grounds 



N. : l°-2° high; leaves oblong-lanceolate; spikes nodding, mostly short; 



flowers greenish-white ; stamens 6 ; akene either flat or obtusely triangular. ®. 



* « * * Leaves heart-shaped or arrow-shaped, petiakd : sheaths half-cylindrical. 



.g *- Tear-thumb. Stems with spreading branches, the angles and petioles armed 



f' with sharp reflexed prickles, by which the plant is enabled almost to climb: 



I flowers in peduncled heads or short racemes, white or flesh-color. ® ' 



P. arif61ilim. Low grounds : leaves halberd-shaped, long-petioled ; the 

 peduncles glandular-bristly ; stamens 6 ; styles 2 ; akene lenticular. 

 4 P. saglttd^tum. Low grounds : leaves arrow-shaped, short-petloled ; the 

 1 peduncles naked; stamens mostly 8 ; styles 3 ; akene sharply 5-angled. 



I -I- ■(- Black Bindweed. Stems twining, not pricldy: flowers whitish, in loose 



' paniclfd racemes : three outermost of the 5 divisions of t!ie calyx keeled or 



crested, at least in fruit : stamens 8 : styles 3 : akenes triangular. 



P. Conv61vulus. Low twining or spreading weed from En., in culti- 

 vated fields, &c. : smoothish, with heart-shaped and almost halberd-shaped 

 leaves, and very small flowers. (T) 



P. cilinbde. Rocky shady places : tall-twining, rather downy, a ring of 

 reflexed bristles at the joints ; leaves angled-heart-shaped ; outer sepals hardly 

 keeled. ^ 



P. dumetdrum, Cumbing False Buckwheat. Moist thickets : tall- 

 twining, smooth ; joints naked ; leaves heart-shaped or approaching halberd- 

 shaped ; panicles leafy ; outer sepals strongly keeled and in fruit irregularly 

 winged, y, 



2. PAGOPYRUM, BUCKWHEA*r. (The botanical name, from the 

 Greek, and the popular name, from the German, both denote Beech-wheat., the 

 grain resembUng a diminutive beech-nut. ) Cult, from N. Asia, for the flour 

 of its grain : fl. summer, (i) 



P. esculdntum, Common B. Nearly smooth ; leaves triangular-heart- 

 shaped inclining to halberd-shaped or arrow-shaped, on long-petioles ; sheaths 

 half-cylindrical ; flowers white or nearly so in corymbose panicles ; stamens 8, 

 with as many honey-bearing glands interposed ; styles 3 ; acutely triangular 

 akene, large. 



P.tart^ricum, Tartart or Indian Wheat. Cult, for flour on our 

 N. E. frontiers and N. : like the other, but flowers smaller and tinged with 

 yellowish ; grain half the size, with its less acute angles wavy. 



3. RHEUM, EHUBAE.B. (Name said to come from the Greek, and to 

 refer to the purgative properties of the root ; that of several species, of N. 

 Asia, yield oflScinal rhubarb.) y. 



R. Rhap6ntieum, Garden R. or Pie-3?i.ant ; 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. 



4. RtlMEX, DOCK, SORREL. (Old Latin name.) The three enlarged 

 sepals which cover the fruit are called valves. Elowers greenish, in whorls 

 on the branches, forming panicled racemes or interrupted spikes. 



§1. Dock. Herbage bitter : fhwers perfect or partly monaxious, in summer. 



« In marshes : stem erect, stout: leaves lanceolate or lance-oblong, flat, not wavy : 

 valves entire or obscurely wavy-toothed in theflrst species. Ij. 



R. orbicul&tus. Great Water Dock. Common N. : 5° -6° high; 

 leaves often l°-2° long; flowers nodding on slender pedicels; the valves 

 round-ovate or almost orbicular, thin, finely reticulated, neariy i' wide, each 

 bearing a grain. ,. , ,,. 



R. Brittonlca, Pale D. Commoner S. : 2° -6° high ; pedicels nodding, 

 shorter than the fruiting calyx, which has broadly ovate loosely reticulated 

 valves, one with a large grain, the others commonly naked ; root yellow. 

 19 



