POLYGONACEAE. 105 



Leaf-blades jointed at the base : ocreae 2-lobed, becoming 



lacerate : filaments, at least the inner, dilated. 2. Polygonum. 



Leaf-blades not jointed at the base : ocreae various, not 2- 

 lobed : filaments slender. 

 Ocreae cylindric, truncate. 



Sepals 4 : calyx curved : stamens 4 or 5. 3. Tov.\ea. 



Sepals 5 : if fewer, the stamens more than 5 : calyx not 



curved. 4. rERSic.\Ri.\. 



Ocreae oblique, more or less open on the side facing the leaf. 

 Herbs various in habit, not vines : sepals neither keeled 

 or winged. 

 Racemes collected into terminal corymbs : embryo 

 dividing the endosperm by an S-shaped curve : 

 plants smooth. 5. Pagopirum 



Racemes not in terminal corymbs : embryo slender, 



at one side of the endosperm : plants prickle-armed. 6. Tracaulon. 

 Vines with twining stems : outer sepals winged or keeled. 7. Tiniaria. 



1. RUMEX L. Annual or perennial fleshy herbs. Leaves alternate, with 

 brittle ocreae. Flowers in panicles, perfect, polygamous, or dioecious, the 

 hypanthium-base conspicuously jointed to the pedicel. Sepals green, 6, un- 

 changed or the 3 inner developing wings, one or all of which usually bear a 

 callosity. Stamens 6. Stigmas peltate, tufted. Achene exserted or included, 

 smooth or granular, usually more or less margined. — Dock. 



Calyx unchanged in fruit: achenes exserted, granular. 1. R. AcctoseUa. 



Calyx accrescent, the inner sepals developing into wings : 

 achenes included, smooth. 

 Sepal-wings entire, more or less undulate. 



Only one of the 3 sepal-wings bearing callosities. 2. R. altissimus. 



All of the 3 sepal-wings bearing callosities. 3. R. crispvs. 



Sepal-wings fringed with spiny teeth. 4. R. oititsifolius. 



1. R. Acetosella L. Plants glabrous, 1-6 dm. tall: blades of the lower leaves 

 2.5-15 cm. long, hastate, the auricles entire or toothed: sepals green, 1 mm. 

 long: achenes ovoid, 3-angled, about 1.5 mm. long. — Common, in fields and 

 dry soil. — Spr. and fall. • — Field-sorrel. Sheep-sorrel. Often a pernicious 

 weed. 



2. R. altissimus Wood. Plants 6-12 dm. tall, the panicle-branches densely 

 flow-ered : lower stem-leaves 1-3 dm. long ; blades lanceolate to oblong-lanceo- 

 late, scarcely crisped: sepal-wings triangular-ovate, 4-5 mm. long, longer than 

 wide, scarcely cordate : achenes about 3 mm. long. — Lower Susquehanna 

 valley. Frequent, on river banks. — Schists. — Spr. — Pale-dock. Peach- 

 leaved DOCK. 



3. R. crispus L. Plants 3-11 dm. tall, the panicle-branches rather closely 

 flowered: lower stem-leaves 1.5-3 dm. long; blades oblong to oblong-lanceo- 

 late, much crisped: flower-clusters contiguous: sepal-wings ovate to orbicular- 

 ovate, 4-5 mm. long: achenes fully 2 mm. long. — Common, in fields and waste 

 places. Nat. of Eu. — Sum. — Curled-dock. 



4. R. obtusifolius L. Plants 6-12 dm. tall, the panicle-branches nearly erect: 

 lower stem-leaves 3-5.5 dm. long; blades oblong to broadly oblong-lanceolate, 

 deeply cordate, somewhat crisped: flower-clusters mostly contiguous, not leafy 

 bracted: sepal-wings ovate-hastate, 4.5-5.5 mm. long, with 3-5 teeth: achenes 

 fully 2 mm. long. — Common, in fields and waste places. Nat. of Eu. — Sum. 



— Bitter-dock. Often a troublesome weed. 



2. POLYGONUM [Tourn.] L. Annual or perennial, erect or prostrate 

 herbs. Leaves alternate, jointed near the top of the ultimately lacerate ocreae. 

 Flowers in axillary clusters which are sometimes aggregated near the ends of 

 the branches. Sepals green to pink or white, the outer ones sometimes cor- 

 rugated in age. Stamens 3-8, often 5-6. Stigmas 3. Achene 3-angled. — Sum. 



— Knotweed. Doorweed. Knotgrass. 



