Jones: Flora of Illinois, 50. Polygonaceae 117 



11. Panicle linear-cylindrical, 3-9 cm. long, the peduncle glandular- 

 hispidulous or strigose; leaves lanceolate, acuminate; wet 

 ground, common. July-Oct. [P. emersum (Michx.) Eaton; 

 P. muhlenbergii (Meisn.) Wats.] P. coccineum Muhl. 



10. Panicle usually several (except in depauperate plants), axillary as 

 well as terminal; plants of moist rich soil. 



13. Sheaths not ciliate. 



14. Panicles erect; glands of the peduncles stipitate; stamens 8 

 or fewer; achenes 2-3 mm. wic'e; cult, ground, roadsides, 



or along streams, common. Aug. -Oct 



P. pennsylvanicum L. 



14. Panicles drooping; glands of the peduncles sessile; stamens 



6; achenes 1.5-2 mm. wide; moist soil, common. July- 

 Sept P- lapathijol'mm L. 



13. Sheaths ciliate. 



15. Stems and peduncles glandular-hispidulous; sandy soil, 



local. Aug.-Sept P. careyi Olney 



15. Stems and peduncles not glandular-hispidulous. 

 16. Sepals glandular-dotted. 



17. Spikes drooping; stamens 4 or 6; achenes dull; 

 along ditches, common. Aug.-Oct. Water-pepper 

 P. hydropiper L. 



17. Spikes erect; stamens 8; achenes glossy; along 



ditches, common. July-Aug. Water Smartweed 

 P. punctatum L. 



16. Sepals not evidently glandular-dotted. 



18. Leaves lanceolate, elliptical, or linear, 0.5-2 cm. 



broad; stems 15-100 cm. tall. 

 19. Plants perennial, native; leaves not dark- 

 blotched; stamens 8; panicles linear, slender, 

 erect, often interrupted at base, 3-8 cm. long, 

 less than 5 mm. thick. 

 20. Leaves strigose on both surfaces, lanceolate; 

 flowers white or pink; swamps, rare. June- 

 Sept P- setaceum Baldw. 



20. Leaves glabrous or nearly so. 



21. Leaves lanceolate; calyx white or pink; 

 achene 2-2.5 mm. long, the tip covered 

 by the calyx; wet ground or in water, 

 common. July-Sept. Mild Water-pep- 

 per P. hydropiperoides Michx. 



21. Leaves linear or linear-lanceolate; calyx 

 greenish white; achene 1.5-2 mm. long, 

 the tip protruding beyond the calyx; 



swamps, s. III., rare 



P. opelousanum Riddell 



