284 SYSTEMATIC BOTANY. 



petioles rounded beneath, channeled above ; flowers very numerous, green- 

 ish white, in fasciculate clusters. Cultivated for its large, acid petioles. 3-6 

 feet high. May.. 



2. Polygonum. Calyx 4-6, mostly 5-parted ; segments often peta- 

 loid, persistent, and inclosing the achenium. Stamens 4-9, mostly 8. 

 Styles 2-3, mostly 3, short, filiform. Achenium mostly triangular. 



1. P. AVICULARE (Knot-grass) Smooth ; stem procumbent, spreading ; 

 branches ascending ; leaves oblong, rough on the margin, acute, sessile, 

 mostly pale green ; stipules short, white, gashed ; flowers nearly sessile, 2-3 

 together in the axils of the leaves, greenish white, sometimes reddish white. 

 In waste grounds, 4/-io' long. June-November. (T) 



2. P. HYDROPIPER (Water Pepper}. Smooth; stem erect or ascending, 

 simple or branching ; leaves lanceolate, entire, acuminate, with pellucid dots, 

 rough on the margin ; stipules inflated, fringed ; flowers pale greenish white, 

 in loose, nodding spikes ; stamens 6-8 ; styles 2-3, united at base ; fruit len- 

 ticular or triangular. In low grounds, 1-2 feet high. August-September. 



3. P. ORIENTALE {Prince's Feather}. Stem tall, erect, branching, some- 

 what hairy ; leaves ovate, upper stipules hairy, somewhat salver-form ; flow- 

 ers large, open, rose-colored, in long, nodding, showy spikes ; calyx 5-parted ; 

 stamens 7 ; style 2-cleft ; fruit lenticular. Cultivated, 4-8 feet high. Au- 

 gust. 



4. P. SAGITTATUM (Arrow-leaved Bindweed). Stem weak, ascending 

 or prostrate, square, with the angles bristly backward ; leaves sagittate, en- 

 tire, acute ; stipules smooth ; flowers small, whitish, in small, terminal heads, 

 on long, slender, smooth peduncles ; stamens mostly 8 ; styles 3 ; fruit 

 acutely 3-angled. In wet grounds, 1-2 feet long. June-August. 



5. P. CONVOLVULUS (Black Bindweed). Stem angular, twining or pros- 

 trate, somewhat rough, naked at the joints ; leaves petiolate, hastate, cordate 

 at base, acute, entire ; stipules nearly entire ; flowers greenish white, some- 

 times tinged with purple, in clusters of 3-4, nodding in fruit ; stamens 8 ; 

 styles 3 ; fruit mostly smooth, triangular. In cultivated grounds, 1-5 feet 

 long. June-September. 



3. Rumex. Calyx persistent ; sepals 6 ; stamens 6 ; styles 3. 

 Stigmas forming a tuft. Achenium 3^angled, covered by the sepals. 



1. R. OBTUSIFOLIUS (Broad-leaved Dock). Stem erect, stout, somewhat 

 rough, branching ; lower leaves ovate, obtuse, cordate at base ; upper ones 

 oblong-lanceolate, acute ; flowers in loose, distant whorls, forming long, 

 nearly naked racemes ; valves sharply toothed at base. Weed in cultivated 

 grounds, 2-4 feet high. July. 



2. R. CRISPUS (Yellow Dock}. Smooth; stem erect, branching; leaves 

 lanceolate, acute, strongly waved on the margin ; flowers in numerous whorls, 

 arranged in crowded racemes, leafless above, forming a large, terminal pani- 

 cle. Root yellow, spindle-shaped. Weed in cultivated grounds, 2-3 feet 

 high. June-July. 



3. R. ACETOSELLA (Sheep Sorrel). Stem erect, leafy, branching; leaves 



