WiEGAXD : Some Species of Bidexs 401 



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There has in the past been considerable discussion regardinjj 

 the occurrence of h}'brids among species of Bidcns and Coreopsis. 

 Every specimen, however, which the w^riter has seen labeled as 

 such differs from one or the other of the supposed 2:)arents only in 

 the direction of the barbs upon the awns. Although hybrids 

 might be expected among these annual plants their occurrence is 

 very doubtful. 



If the direction of the barbs is not constant among the indi- ' 

 viduals of one species this character can obviously not be used for 

 the separation of the genera Coreopsis and Bidens^ a fact which has 

 already been strongly emphasized by Dr. Britton. Indeed, a num- 

 ber of species of Coreopsis are evidently Bidens except for their 

 barbs. The transferrence of these species to the genus Bidens 

 becomes therefore necessary for a correct interpretation of the two 



genera. 



The section Platvcarpae, the principal members of which are 

 here treated, should therefore consist of the following species in 

 northern North America : B. frondosa, B. melauoearpa, B. dis- 

 coidea^ B, connata, B. coniosa, B. bidentoides^ B. dentata, B. cenina, 

 B, laevis, B. Nashii, B, coronata, B. triehosperma^ B. aristosa, and 

 B. invohicrata. 



The writer wishes to thank Dr. Robinson for kindly loaning 

 the material in the Gray Herbarium, and Dr. Small for loaning 



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that in the Herbarium of Columbia University; also the New 

 England Botanical Club for the opportunity of studying a large 

 amount of material from the vicinity of Boston ; and especially Mr. 

 E. P. Bicknell, a critical student of this group, who has generously 

 furnished valuable suggestions and extensive notes upon many of 

 the species. ^ i 



yiiopsiH of tlie Species 



A. Achenes upwardly barj:»ed en the margins ; corolla 4-5-toothed ; awns 2 ; rays small 



or none. 

 Outer involucral bracts 4-S, inner oblong, equaling the disk or longer; ovaries of 



the ray-flowers hairy, minutely awned ; achenes narrow, nearly black, hairy, 

 papillose or tuberculate, rarely smooth, mai^ins upwardly barbed to base of 

 awns. 

 Corolla stramineous, 4-toothed ; achenes long and ver}' narrow, awns filiform, 

 upwardly barbed ; leaves simple ; outer involucral bracts 4-5, inner longer 



than the achenes. 



I. B. bidentoides. 



Corolla orange, 5-toothed ; achenes of ordinary form ; leaves pinnate; inner 

 involucre equaling the achene. 



