420 polygonace^e. (buckwheat family.) 



heart-shaped nearly entire valves bearing a small grain, or its midrib thickened 

 at the base, was found spontaneous at Amherst, Mass., by Prof. Tuckerman, in 

 the form with undulate leaves, R. orientalis, Bcnih. (Adv. from Eu.) 



2. R. longif6lics, DC. (R. dome'sticus, Hartm., and too near. R. aqua t- 

 icus, L.), known by the rounded somewhat heart-shaped valves all without a 

 grain, — is indigenous at the northwest, perhaps in Northern Wisconsin. (Eu.) 



■*- Valves (smaller) one or more of them conspicuously grain-bearing. 

 ++ Indigenous : leaves not wavy, none heart-shaped, except the lowest of No. 6. 



3. R. orbieulatus, Gray. (Great Water-Dock.) Tall and stout 

 (5° -6° high); racemes upright in a large compound panicle, nearly leafless; 

 whorls crowded ; pedicels capillary, nodding, about twice the length of the fruiting 

 calyx ; the valves orbicular or round-ovate, very obtuse, obscurely heart-shaped at 

 base, membranaceous, finely reticulated, entire or repand-denticulate (2" -3" 

 broad), all grain-bearing; leaves oblong-lanceolate, rather acute at both ends, 

 transversely veined, and with obscurely erose-crenulate margins (the lowest, in- 

 cluding the petiole, l°-2° long, the middle rarely truncate or obscurely cordate 

 at base) . ( R. Hydrolapathum, var. ? Americanus, Ed. 2. R. Britannica, Pursh ? 

 Bigeloiv, Torr. Fl. N. Y. R. aquaticus, Pursh ?) — Wet places : rather common 

 northward. — Root yellow. Leaves occasionally abruptly contracted a little be- 

 low the enlarging apex. Valves very much rounder, thinner, larger in propor- 

 tion to the grain, and more reticulated than in the European R. Hydrolapathum, 

 resembling those of R. longifolius except in bearing a conspicuous grain. 



4. R. Britannica, L. (Pale Dock.) Rather tall (2°-6° high); ra- 

 cemes spike-like and panicled, nearly leafless ; whorls crowded ; pedicels nodding, 

 shorter than the fruiting calyx ; the valves broadly ovate or obscurely heart-shaped, 

 obtuse or acutish, entire, membranaceous, loosely reticulated (about 2" broad), 

 one with a conspicuous grain, the others with a small grain or thickened midrib, 

 or naked ; leaves ovate-lanceolate or oblong-lanceolate, acute, pale, thickish, obscurely 

 veiny (those of the stem 3' - 6' long, contracted at base into a short petiole), none 

 heart shaped. (R. Claytonii, Campdera, which name is to be adopted if we 

 reject that inconsiderately assigned by Linnaeus, who transferred the obscure 

 Herba Britannica of the old writers to a Virginian species. R. xanthorhizus, 

 Hoffmansegg , ex Meisner. R. altissimus, Wood. ) — Moist grounds, New York 

 to Illinois and southward. 



5. R. salicifblius, Weinmann. (White Dock.) Rather low (l°-3° 

 high); root white; leaves narrowly or linear-lanceolate, or the lowest oblong; 

 whorls much crowded; pedicels much shorter than the fruiting calyx; valves deltoid- 

 ovate, obtusish or acutish (about 1^" long), one, two or sometimes all three with 

 a conspicuous often very large grain : otherwise nearly as in the preceding. (R. 

 pallidus, Bigeloiv.) — Salt marshes, coast of New England; also far westward 

 and northward. 



6. R. verticillatus, L. (Swamp Dock.) Rather tall (3°-5° high); 

 racemes nearly leafless, elongated, loose ; the whorls crowded or the lower ones 

 distant; fruit-bearing pedicels slender, club-shaped, abruptly reflexed, 3-4 times 

 longer than the fruiting calyx ; the valves dilated-rhomboid, obtusely someivhat pointed, 

 strongly rugose-retiadated, each hearing a very large grain; leaves lanceolate or 



