88 Order CARYOPHYLLACE# 
Ocreae fringed with marginal bristles. 
Racemes drooping, interrupted; calyx green, punctate. 
9. P. hydropiper. 
Racemes erect. 
Achenes lenticular or three angled, styles 2 or 3. 
Styles parted to near the base. 
Calyx rose-colored; achene 2 mm. long; perennial. 
7. P. persicarioides. 
Calyx green; achene 2.5 mm. long. 
10. P. punctatum. 
Styles parted to about the middle. 
Annual, often glabrous; leaves usually with a 
dark blotch near the center. 6. P. persicaria. 
Perennial, strigillose; usually growing in wet 
soil. 8. P. hydropiperoides. 
Racemes interrupted, flowers a cm. apart. 11. P. virginianum. 
Leaves small, not over 5 cm. long and generally much less. 
Fruit not reflexed. 
Achenes 2-3 mm. long, little if at all exserted. 
Plants decumbent. 
Leaves mostly acute; achenes 2 mm. long. 
12. P. aviculare. 
Leaves mostly obtuse; achenes 3 mm. long. 
13. P. buxiforme. 
Plants erect or ascending. 
Leaves oval or ovate; flowers one or two in each axil. 
14. P. erectum. 
Leaves lanceolate or linear-lanceolate; flowers several 
together in the axillary clusters. 
Stems terete; achenes reticulated. 
Flowers larger, 2-3 mm. long, exceeding the 
stipules. 15. P. ramosissimum. 
Flowers small, less than 2 mm. long, exceeded by 
the frayed stipules. 16. P. prolificum. 
Stems 4-angled, very slender; leaves plicate. 
18. P. tenue. 
Achenes 5-6 mm. long, exserted. 17. P. exsertum. 
Fruit reflexed; perianth 4-5 mm. long. 19. P. douglassii. 
Climbing vines; outer calyx lobes keeled or winged in fruit. 
Outer calyx lobes merely keeled; achenes 3 mm. long. 
20. P. convolvulus. 
Outer calyx lobes winged and decurrent in fruit; achenes 4-5 
mm. long. 21. P. scandens. 
Stems with recurved prickles. 22. P. sagittatum. 
1. Polygonum amphibium L. Water Smartweed. 
In water or sometimes in muddy places. Cherry county; Peru; 
Richardson county; Swan Lake; Thedford; Valentine; Whitman. 
2. Polygonum muhlenbergii (Meisn.) Wats. 
In wet places and in shallow water. Cherry county; Emerson; Ken- 
nedy; Richardson county; Whitman. 
3. Polygonum lapathifolium L. 
A common weed in the eastern part of the state, less common in the 
western part. Dawes county; Kennedy; Lincoln; Long Pine; Mullen; 
get Paddock; Red Cloud; Riverton; Talmage; Weeping Water; 
itman. . 
