BUCKWHEAT FAMILY. 289 



P. Hydr6piper, Commoit S. or Watee Pepper. Low or wet grouuda 

 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. 

 *- Teae-thumb. Steins with spreading brandies, the angles and petioles armed 

 with sharp reflexed prickles, bg which the plant is ennbled almost to climb : 

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

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

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



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

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



•I- -1- Black Bindweed. Stems twining, not prickly : flowns whitish, in loose 

 panicli'd racemes : three outermost of the 5 divisions of Ike calyx keeled or 

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



P. Convolvulus. Low twining or spreading weed from Eu., in culti- 

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

 leaves, and very small flowers. ® 



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

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

 keeled. Jl 



P. dumetbruin, 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 grain : fl. summer. @ 



P. eseul6ntum, Common B. Nearly smooth ; leaves triangular-heart- 

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

 halt-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^rlcum, Taetakt 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. (iSTame said to come from the Greek, and to 

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

 Asia, yield officinal rhubarb.) 2/. 



R. Rhapdntlcum, Gaeden 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. RiJMEX, DOCK, SORREL. (Old Latin name.) The ihree 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: flowers perfect or partly monoecious, in summer. 



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

 valves entire or obscureltj wavy-loothed in the first species. "1). 



R. orbioulktus, Geeat Watee 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 i' wide, each 

 bearing a grain. 



R. Britanniea, 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 



