POLYGONACE.E. (BUCKWHEAT FAMILY.^ 375 



nium lenticular : annuals, with heart-shaped or arrow-shaped petioled leaves ; 

 sheaths semicylindrical. 



* Stems flaccid, not twining, but somewhat climbing or supported on other plants by 

 the reflexed prickles which beset the angles of the stem and petioles : divisions of the 

 (pale rose-colored or white) calyx not keeled: bracts chaff-like. 



16. P. arifolium, L. (HALBERD-LEAVED TEAR-THUMB.) Stem grooved- 

 angled; leaves halberd-shaped, taper-pointed, long-petioled ; flowers somewhat ra- 

 ccmed (few) ; peduncles glandular-bristly ; calyx often 4-parted ; stamens 6 , 

 styles 2, very short; fruit lenticular (large). Low grounds. Aug. 



17. P. sagittffitum, L. (ARROW-LEAVED TEAR-THUMB.) Stem 4- 

 angled; leaves arrow-shaped, short-petioled ; flowers capitate; peduncles smooth; 

 stamens mostly 8 ; styles 3, slender ; fruit sharply 3-angled. Low grounds ; com- 

 mon. July - Sept. Slender, smooth except the angles of the stem and midrib 

 beneath : these are armed with a line of fine and very sharp saw-toothed prickles, 

 which cut the hand drawn against them. 



# * Stems twining, not prickly : calyx (greenish tinged with white or rose-color) with 

 the 3 outer divisions keeled, at least in fruit : flowers in loose panicled racemes : 

 bracts like the stipules. 



18. P. CONVOLVULUS, L. (BLACK BINDWEED.) Stems twining or pro- 

 cumbent (l-2 long) , roughish, the joints naked; leaves halberd-heart-shaped, 

 pointed ; flowers in small interrupted corymbose racemes ; outer calyx-lobes keeled; 

 fruit smoothish. Cultivated and waste grounds ; common. July, Aug. (Nat. 

 from Eu.) 



19. P. CilillOtlO, Michx. Minutely downy ; the sheaths fringed at the bas<* 

 with reflexed bristles ; leaves heart-shaped and slightly halberd-shaped, taper 

 pointed; racemes panicled; calyx-lobes obscurely keeled; fruit very smooth anc* 

 shining. Copses and rocky hills; New England and Penn. to Wisconsin, anc 

 northward. July - Sept. Stems climbing 3 - 9 high. 



20. P. dumetoruni, L. (CLIMBING FALSE BUCKWHEAT.) Smooth; 

 theaths naked; leaves heart-shaped or slightly halberd-shaped, pointed; racemes 

 interrupted, leafy ; the 3 outer calyx-lobes strongly keeled and in fruit winged, the 

 wings often broad, sometimes very narrow; fruit smooth and shining. (P. scan- 

 dens, L.) Moist thickets; common. Aug. Stems twining 8 -12 high 

 over bushes. (Eu.) 



2. FAGOPYRUM, Tourn. BUCKWHEAT. 



Calyx petal-like, equally 5-parted, withering and nearly unchanged in fruit. 

 Stamens 8. Styles 3 : stigmas capitate. Achenium 3-sided, longer than the 

 calyx. Embryo large, in the centre of the albumen which it divides into 2 parts, 

 with very broad and foliaceous plaited and twisted cotyledons. Annuals, with 

 triangular-heai't-shaped or halberd-shaped leaves, semicylindrical sheaths, and 

 corymbose racemes or panicles of white flowers, often tinged with green or rose- 

 color. (Name fay 6s, the beech, and irvpos, wheat, from the shape of the grain 

 being that of the beech-nut; whence also the English name Z^ur/jwheat. from 

 the German 33uc1)e, beech.) 



