The Flora of the Cayuga Lake Basin 413 



[I. SALICINA L. 



Wooded bank at South Ave. bridge, Cascadilla Creek, Ithaca, 1925 (Mrs. M. W . 

 Allen). Native of Eu.] 



13. Polymnia L. 



a. Rays 12-25 mm. long, yellow ; leaves pahnately veined and lobed ; achenes 

 striate; plants not glandular. 1. P. uvedalia 



a. Rays 10 mm. long or less, whitish ; leaves pinnately lobed ; achenes 3-ribbed ; 

 plants glandular. 2. P. canadensis 



1. P. uvedalia L. Leafcup. 



Rich low woodlands and banks ; rare. Aug. 



"Salmon Cr. ravine, below the spring" (£>.) ; "Big Gully, above the Falls" (A!). 

 N. Y. to Ind., southw. to Fla., Mo., and Tex.; rare or absent on the Coastal Plain. 

 A plant of the rich soils of the Ohio and Mississippi Valleys. 



2. P. canadensis L. Leafcup. 



Wooded slopes and bottom-lands, in limy regions ; scarce. Aug. 



Slope of North Pinnacle, Caroline (D.\) ; Enfield Glen; Negundo Woods (D.) ; 

 lower Six Mile Creek; ravine of Ferris Brook (£>.!); ravine near Elm Beach, 

 Romulus; Paine Creek; Grove Creek; cedar swamp in Tyre (£>.). 



W. Vt. to Minn., southw. to N. C, Tenn., and Ark. ; rare or absent on the Coastal 

 Plain. A plant primarily of the Mississippi Valley. 



[Parthenium L.] 

 [P. Hysterophorus L. 



Several plants of this species were found growing on the city garbage dump along 

 the lighthouse road, Ithaca, in 1921. Native of tropical Am.] 



14. Ambrosia (Tourn.) L. 



a. Leaves large, 3-lobed ; plant 1-6 m. high ; receptacle of staminate heads naked. 



1. A. trifida 



a. Leaves 1-2-pinnatifid ; plant 0.3-2.5 m. high ; receptacle of staminate heads chaffy. 

 b. Leaves 2-pinnatifid, thin ; fruit with about 6 tubercles. 2. A. artemisiifolia 



b. Leaves 1-pinnatifid, thick; fruit almost without tubercles. [A. psilostachya] 



1. A. trifida L. Great Ragweed. 



Rich alluvial soils about streams and marshes ; locally common. July 15-Aug. 



In the Cayuga Lake Basin, confined to the Cayuga Lake marshes and the inlet 

 region. 



Que. to Man., southw. to Fla., Nebr., Colo., and N. Mex. ; occurring sparingly 

 along the coast. 



2. A. artemisiifolia L. (Including A. elatior L.) Common Ragweed. 



Dry fields, roadsides, and waste places, in various soils; very common. Aug. 15- 

 Sept. 15. 



N. S. to B. C, southw. to Fla. and Mex., including the Atlantic Coastal Plain. 

 The native range is now obscure, but the species was probably not indigenous east of 

 the Allegheny Mts. 



This plant is believed to be the principal cause of autumnal hay fever. The pol 

 lens of this and other species of Ambrosia, as well as that of Tva, are equally vim 

 lent. 



