110 POLYGONACEAE. 



Plants with the upper leaves more scattered and reduced, mostly erect perennials. 

 Upper bracts not subulate ; achenes dull. 



Lobes of the perianth with yellowish margins ; perianth 3-4 mm. long ; 

 achenes about 3 mm., nearly smooth. 4. P. ramosissimum. 



Lobes of the perianth with whitish or pinkish margins ; perianth 2-3 mm. 

 long ; achenes 2-2.5 mm. long, distinctly granulate or striate. 



5. P. rubescens. 



Upper bracts subulate ; achenes smooth and shiny. 6. P. sawatchense. 



Inflorescence aggregated at the ends of the branches ; bracts leaf-like and usu- 

 ally broader than the narrowly linear leaves ; plants dwarf annuals. 

 None of the perianth-lobes keeled. 



Leaves several, gradually merging into the bracts ; achenes blunt-angled and 



strongly striate. 7. P. Watsonii. 



Leaf usually solitary and much longer than the bracts ; achenes sharp-angled 



and obscurely striate. 8. P. unifolium. 



Some of the perianth-lobes keeled near the apex. 9. P. Kelloggii. 



Fruit reflexed. 



Upper bracts much reduced and subulate. 



Perianth 1.5-2 mm. long; leaves narrowly linear; achenes exerted. 



10. P. Engelmannii. 

 Perianth 4-5 mm. long ; lower leaves oblanceolate to linear-oblanceolate ; 



achenes included. n. P. Douglasii. 



Upper bracts foliaceous, relatively broad, lanceolate or oblong. 



Achenes included. 12. P. montanum. 



Achenes exserted. 13. P. commixtum. 



1. Polygonum erectum L. In waste places from Me. and Alb. to Ga. and 

 Ark. and Kans. Also reported from Colorado, but no exact locality given. 



2. Polygonum buxiforme Small. (P. litoralc Small, in part) In sandy 

 and alkaline soil from Ont. and Wash, to Va., Tex. and Nev. Alt. 4000-10,000 

 ft. Georgetown; Silver Plume; along Platte River, Denver; Montrose; Fort 

 Collins; Colorado Springs. 



3. Polygonum aviculare L. In waste grounds from Newf. and Sask. to 

 Va. and Calif.; introduced from Europe. Alt. 4000-8000 ft. Fort Collins; 

 Gunnison. 



4. Polygonum ramosissimum Michx. In river valleys and low ground from 

 Minn, and Wash, to Ills., N. M. and Nev. Alt. 4000-10,000 ft. Cheyenne 

 Mountain ; Fort Collins ; Upper La Plata Canon. 



5. Polygonum rubescens Small. In sandy soil from Ida. to Colo, and Utah. 

 Alt. 4500-8000 ft. Parlin, Gunnison Co. ; Larimer Co. 



6. Polygonum sawatchense Small. On hillsides from S. D. and Wash, to 

 Colo., Ariz, and Calif. Alt. 4000-9000 ft. Saguache Range ; Box Canon, 

 west of Ouray ; Calhan ; Veta Pass ; Estes Park. 



7. Polygonum Watsonii Small. (Polygonum imbricatum S. Wats.) In wet 

 places from Mont, and Wash, to Colo, and Calif. Alt. 6000-10,000 ft 

 South Park; Leroux Park; Upper West Mancos Canon; Chambers' Lake. 



8. Polygonum unifolium Small. In wet places from Mont, to Colo. Ten- 

 nessee Pass. 



9. Polygonum Kelloggii Greene. In wet soil from Wash, and Mont, to 

 Calif. Alt. 6000-10,000 ft. Steamboat Springs ; Bard Creek Valley, near 

 Empire. 



10. Polygonum Engelmannii Greene. (P. tcnuc microspcrmum Engelm.) 

 On hillsides and mountains from Mont, and B. C. to Colo. Alt. 5000-10,000 



