POLTGONACE^. (BUCKWHEAT FAMILY.) 375 



nium lenticuJan annuals, with heart-shaped or arrow-shaped petiekd leaves: 

 sheaths semitylindrical. 



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

 the reflexed pricJdes 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. arifdliiim, L. (Halbbrd-leavep Tear-thumb.) Stemgrooved- 

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

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

 styles 2, very short; fi-uit lenticular (large). — Low grounds. Aug. 



17. P. sagittatum, L. (Arrow-leaved Tear-th0mb.) Stem 4- 

 angted; 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 tlie 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. Conv6lvulus, L. (Black Bindweed.) Stems twining or pro- 

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

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

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

 from Eu.) 



19. P. Cilinode, Michx. Minutely downy ; the sheaths fringed at the hase 

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

 pointed; racemes panicled; calyx-lobes cbscurdy keeled; fruit veiy smooth and 

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

 northwai-d. July - Sept. — Stems climbing 3° - 9° high. 



20. P. dumetoruin, L. (Climbing False Buckwheat.) Smooth; 

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

 ihterrupted, 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. FAGOP'K'RirM, Toum. 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 

 ti'iangnlar-heart-shapcd or halberd-shaped leaves, semicylindrical sheaths, and 

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

 color. (Name <pr]y6s, the beech, and Trvpos, wheat, from the shape of the grain 

 being that of the beech-nut ; whence also the English name BuckvfhesA, from 

 the Grerman 3SttCJ)e, beech.) 



