412 WiF/iAXD: Some Species ok Hidens 



B, conw^a Is distinguished from all other Anierican representa- 

 tives of the germs by its broad, 3-awned, retrorsely margined 

 achenc ; from B. connata it differs also b}' its short branches, stout 

 peduncles, pale leaves, very foliaceous in\'olucrc of usually more 

 numerous bracts^ and long pale 4-toothcd corolla with included 

 stamens; from B, bidentoidcshy the three downward-barbed awns . 

 and flat rctrorse achcnes ; and from B. ccriiuiis by the 5 -toothed 

 corolla, included stamens, 4-awned and angled achene, and by the 

 erect heads. The flowering" period is from September 1st to Oc- 

 tober 1st. 



Its closest affinity is however with B. tripartita intcgra Koch 

 (3-awned) a nati\'e of central Europe. Tliis variet}' can be distin- 



I 



guished from the ** second growth'' American plants only by the 

 slightly shorter involucre, smaller, slightly narrower, and thicker 

 achenes with shorter awns. Throucfh B. trit^artita the American 

 plant is connected with l3, ' froiidosa and B. couiata^ and through 

 B, platyccpliala of Europe with B, ccrniia. 



6, Bidens dentata (Xutt.) 



B. cJirjsafithonoidcs Hook. Fl. Bor. Am. i : 314. 1S33. 



r 



(According to T. & G.) Not of Michx. 



B. quadriaristata dentata Nutt. Trans. Amer. Phil. Soc. 11. 7: 



^6^, 1841. 



B, cti')iua data T. & G. Fl. N. A. 2 : 352. 1842. 



Stem very stout (40-100 cm.), glabrous or sparsely hirsute, 

 branches short or the upper longer and ascending : leaves pale, 

 often very large (8-18 cm. long), broadly lanceolate, oblanceolate, 

 or oval, acute or short acuminate, contracted at the nearly sessile 

 base, coarsely serrate, incised or rarely even parted, upper leaves 

 nearly as large : heads {c\w (1-3), large and nearly sessile, broader 

 than high (20 mm. diam.) ; outer involucral bracts about 8, linear to 

 oblanceolate, usually longer than the head, very unequal, some 

 often very foliaceous and incised, conspicuously ciliatc below ; 

 inner bracts elliptic-ovate, acutish ; ray flowers preseiU, ligule one 

 half longer than the disk, oval, pale yellow, the ovary broadly 

 oblong, glabrous except the strongl}' retrorse margins, awnless : 

 corolla of the disk flowers large (4-5 mm.) funnclform, gradually 

 contracted below, 5 -toothed, deep yellow : achenes large and rather 

 broad (3x8 mm.), flat, glabrous, brownish, broadl}' cuneate, slightly 

 contracted at the summit ; margins spar<fely retrorse with small 

 barbs the lowermost of which are often erect, summit concave : 



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