146 CONTRIBUTIONS FROM TPIE NATIONAL HEEBAEIUM. 



Spikes several or numerous. 

 Ocreaj not fringed witli bristles. 



Flowers white, greenish, or pink, borne in slender, elongate, usually drooping 



spikes 2-8 cm. long 3. P. lapathifolia. 



Flowers deep pink or rose-colored , borne in thick oblong-cylindric erect spikes 



2-5 cm. long 4. P. pennsylvanica. 



Ocreae fringed with bristles. 



Sepals conspicuously gland-dotted. 



Spikes drooping; stamens 4 or 6; achene granular and dull 6. P. hydropiper. 



Spikes erect; stamens 8; achene smooth and shining 6. P. punctata. 



Sepals not gland -dotted . 

 Plants up to 2.5 meters high, coarse; ocrese often with a spreading herbaceous 

 border; leaves long-petioled, the blades broad, ovate or oblong; spikes 



drooping 7. P. orientalis. 



Plants 20-100 cm. high; ocrese without a spreading border; leaves sessile or nearly 

 so, the blades narrow, linear-lanceolate to oblong-lanceolate; spikes erect. 

 Plants annual; spikes short-cylindric, dense. Leaves usually with a dark 



triangular or crescent-shaped spot near the middle 8. P. mitis. 



Plants perennial; spikes slender, often interrupted 9. P. hydropiperoides. 



1. Persicaria amphibia (L.) S. F. Gray. Willow-weed. 

 Aquatic; two collections on the Potomac flats between the Outlet Lock and Ead's 



Mill. Midsummer. Widely distributed in N. Amer. {Polygonum hartwrightii A. 

 Gray; P. amphibiicm L.) 



2. Persicaria muhlenbergii (S. V/ats.) Small. 



River banks and other moist situations; not uncommon. Aug.-Sept. Widely 

 distributed in N. Amer. {Polygonum cmersum Britton; P. ampfdbium terrestre of 

 Ward's Flora; P. muhlenbergii S. Wats.) 



3. Persicaria lapathifolia (L.) S. F. Gray. Willow-weed. 

 Low waste places; common, especially on the Potomac Flats. July-Sept. Through- 

 out N. Amer. {Polygonum incornatum Ell.; P. lapathifolium L.) 



4. Persicaria pennsylvanica (L.) Small. 



Wet places generally; common. July-Sept. Eastern N. Amer. {Polygonum 

 pennsylvanicum L.) 

 6. Persicaria hydropiper (L.) Opiz. Smartweed. 



Low moist situations; locally common. July-Sept. Nearly throughout 1^. Amer.; 

 naturalized from Eur. {Polygonum hydropiper L.) 



6. Persicaria punctata (Ell.) Small. Smartweed. 

 Swamps and moist alluvial situations; common. July-Sept. Nearly throughout 



N. Amer. {Polygonum punctatum Ell.) 



7. Persicaria orientalis (L.) Spach. Prince's-feather. 

 Waste places; not uncommon, particularly along the Canal and on the Potomac 



Flats. July-Sept. Native of India; escaped from gardens and naturalized in the 

 eastern U. S. {Polygonum orientale L.) 



8. Persicaria mitis Gilib. Lady's-thumb. Pinkweed. 

 Moist waste places; common, especially along the river. June-Sept. N. Amer. 



and Eur. {Polygonum persicaria L.; Persicaria persicaria Small.) 



9. Persicaria hydropiperoides (Michx.) Small. 



Wet alluvial situations; several stations along the Potomac, but not common. 

 Aug.-Oct. N. Amer. {Polygonum hydropiperoides Michx.) 



5. BILDERDYKIA Dum. 



Plants annual; outer sepals keeled at maturity 1. B. convolvulus. 



Plants perennial; outer sepals conspicuously winged at maturity. ..2. B. scandens. 



