DICOTYLEDONOUS PLANTS 67 



reflexed at maturity. Calyx green, the valves broadly triangular, 

 abruptly pointed, reticulated, a distinct long and narrow tubercle on 

 the back of each. Swamps and wet ground.* 



3. R. crispus, L. YELLOW" DOCK. Stout, smooth, 3-4 ft. high. 

 Leaves lanceolate, margins very wavy, acute, the lower more or less 

 heart-shaped. Root long, tapering gradually downward, yellow, 

 very tough. Flowers in whorls crowded in long, straight, slender 

 racemes. Valves roundish heart-shaped, mostly tubercled. A very 

 hardy weed, introduced from Europe. 



II. POLYGONUM, L. 



Annual or perennial, terrestrial or aquatic herbs, with 

 enlarged joints and simple, alternate, entire leaves ; the 

 sheathing stipules often cut or fringed. Flowers perfect, 

 usually white or rose-colored, each flower or cluster subtended 

 by a membranaceous bract, similar to the stipules of the 

 leaves. Calyx mostly 5-parted, the divisions petal-like, erect 

 and persistent. Stamens 3-9. Styles 2-3-parted. Fruit 

 lens-shaped or 3-angled.* 



1. P. aviculare, L. KNOT-GRASS. Annual or perennial. Stem 

 prostrate or ascending, diffuse, smooth, 6-24 in. long. Leaves small, 

 lanceolate or linear-oblong, obtuse, nearly 



or quite sessile. Stipules thin and dry, 2-3- 

 cleft or cut. Flower-clusters axillary, 1-5- 

 flowered, flowers inconspicuous, nearly ses- 

 sile. Calyx greenish-white, 5-parted, the 

 lobes with white or colored borders. Stamens 

 5-8. Style 3-parted ; akene 3-angled, not 

 shining. A common weed in dooryards and A B 



where the ground is trampled.* FIG. 10. Buckwheat. 



2. P. DumetOrum, L. FALSE BUCK- A, flower, longitudinal sec- 

 WHEAT. Perennial ; stems slender, twining, tion '> B > fruit ( both some - 

 branched, 2-10 ft. long. Leaves ovate, ^ - lar g ed >- 

 taper-pointed, heart-shaped to halberd-shaped at the base, long- 

 petioled. Stipules cylindrical, truncate. Flowers in axillary, more 

 or less compound and leafy racemes. Calyx greenish-white, the 

 outer lobes winged and forming a margin on the pedicel. Stamens 

 8. Stigmas 3 ; akene 3-angled, black, smooth, and shining. Margins 

 of fields and thickets.* 



