BUCKWHEAT FAMILY. 289 



P. Hydr6piper, 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, petioled : sheaths half-cylindrical. 

 ^- Tear-thumb. Stems with spreading brandies, the angles and petioles armed 



with sharp reflexed prickles, by wfiich the plant is enabled almost to climb : 

 flowers in peduncled heads or short racemes, white or flesh-color. Q) 

 P. arifblium. Low grounds : leaves ha)berd-sh.aped, long-petioled ; the 

 peduncles glandular-bristly ; stamens 6 ; stales 2 ; akene lenticular, 



P. sagitt&tum. Low grounds : leaves arrow-shaped, short^petioled ; the 

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



■**- ■*- Black Bindweed. Stems twining, Twt prickly :■ flowers whitish, in loose 

 panicled racemes : three outermost of the 5 divisions of the calyx keeled or 

 crested, at least in fruit : stamens 8 : styles 3 : akenfs triangular, -■ 



P. Convdlvulus. Low twining or spreading weed from Eu., in ctilti- 

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

 leaves, and very small flowers. ® 



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. dumetbrum, Climbing 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, "ij. 



2. PAGOPYRUM, BUCKWHEAT. (The botanical name, from the 

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

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

 of its gi'ain : fl. summer. @ 



F. escul^ntum, 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^icum, 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, RHUBARB. (Name said to come from the Greek, and to 

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

 Asia, yield officinal rhubarb.) % 



R. Rtiapdllljicuin, 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. 



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

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

 on the branches, forming panicled racemes or interrupted spikes. 



§ 1. Dock. Herbage bitter : flowers perfect or partly monoecious, in summer. 



* In marshes ; stem erect, stout : leaves lanceolate or lance-oblonfi, flat, not wavy : 



valves entire or obscurely wavy-toothed in the first species. 2/ 



R. orbicul&tVLS, 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, nearly j' w;ide, each 

 bearing a grain. 



R. Brit^nnica, 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 yello^. 

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