106 POLYGON ACE AE. 



Flower-clusters separate, scattered more or less throughout the plant. 



Sepals with white, pink, or purplish margins : plants mainly prostrate, pale, 

 bright- or bluish-green. 1. p. neylectum. 



Sepals with yellowish-green margins : plants mainly diffuse, 



yellowish-green. 2. P. erectum. 



Flower-clusters approximate on the branches, forming long, 



raceme-like panicles : plants erect. 3. P. tenue. 



1. P. neglectum Besser. Plants bright- or bluish-green, the branches ulti- 

 mately prostrate or procumbent, 1-6 dm. long: leaf -blades thin, narrowly 

 elliptic, elliptic-lanceolate, or linear, less than 2 cm. long,, acute or acuminate: 

 ocreae very thin: sepals about 1.5 mm. long: achenes about 2 mm. long. 

 Common, about dwellings, and on roadsides and in waste places. Nat. of Eu. 



2. P. erectum L. Plants yellowish-green, the branches spreading or decum- 

 bent, 1-12 dm. long: leaf -blades much larger than in the preceding species, 

 mainly 2-6 cm. long, oblong, elliptic, oval, or somewhat broadened upward: 

 ocreae rather sordid: sepals about 3 mm. long, often corrugated in age: 

 achenes 2.5-3 mm. long, dull. Common, about dwellings, in waste places and 

 on moist banks. 



3. P. tenue Michx. Plants 1-4 dm. tall, the branches wiry: leaf -blades 

 linear to linear-lanceolate, 0.5-3 cm. long, each with 2 lateral impressions on 

 either side of the midrib: flowers short-pedicelled: sepals becoming 2.5-3 mm. 

 long : achenes ovoid, 2.5-3 mm. long. Common, in dry places or rocky soil. 



3. TOVARA Adans. Annual erect herbs. Leaves alternate, not jointed 

 at the fringed ocreae. Flowers in lax remote clusters borne on virgate branches. 

 Sepals more or less colored, 4, the 2 lateral ones overlapping the others. 

 Stamens 4, and alternating with the sepals, or 5, the fifth one opposite the 

 lower sepal: filaments slender. Stigmas 2. Achene lenticular. 



1. T. virginiana (L.) Adans. Stem strigose, 3-14 dm. tall, virgately 

 branched or simple: leaf -blades ovate to ovate-lanceolate, 3-16 cm. long: 

 sepals ovate to rhombic-ovate, 3-3.5 mm. long: styles longer than the ovary: 

 achenes 3.5-4 mm. long, ovoid or ovoid-oblong, invested in the nodding calyx. 



Common, on shaded banks and in thickets. Sum. 



4. PERSIC ARIA [Tourn.] Adans. Annual or perennial, erect or spread- 

 ing herbs. Leaves alternate, not jointed at the cylindric naked or fringed 

 ocreae: blades narrowed at the base. Flowers borne in spike-like panicles. 

 Sepals white or colored, 5, neither winged nor keeled. Stamens 4-8: filaments 

 slender. Stigmas 2 or sometimes 3. Achenes lenticular or 3-angled, included. 



Sum. 



Raceme usually solitary and terminal : plants mainly aquatic. 



Leaf-blades more or less acuminate at the apex, pubescent : panicles long and 



slender. 1. P- Muhlenbergii. 



Leaf-blades obtuse or merely acute at the apex, glabrous : 



panicles short and stout. 2. P. amphibia. 



Racemes several or numerous : plants mostly terrestrial. 

 Ocreae naked or fringed, not spreading at the top : coty- 

 ledons accumbent. 

 Ocreae truncate and naked at maturity. 



Racemes erect : achenes orbicular or wider than 



long. 3. P. pennsylvanica. 



Racemes drooping or with drooping tips : achenes 



broadly oblong or ovoid. 4. P. lapathifolia. 



Ocreae fringed with bristles. 



Panicles short, stout, compact. 5. P. Persicaria. 



Panicles slender, elongate, lax or interrupted. 



Calyx not glandular-punctate. 6. P. hydropiperoides. 



Calyx glandular-punctate. 



Panicles erect : achenes smooth, shining. 7. P. punctata. 

 Panicles drooping : achenes granular, dull. 8. P. Hydropiper. 

 Ocreae with spreading fringed tops : cotyledons incumbent. 9. P. orientalis. 



