504 BOTAXICAL GAZETTE [jtjne 



with a careful examination of a vast amount of B. cernua material 

 from different American and European stations, has convinced me 

 only the more of the utter impossibility of separating the many 

 forms as species. Scarcely a form occurs in the United States that 

 is not duplicated by a precisely similar form in Europe. Even 

 Greene himself (loc. cit. 252) was compelled to declare "after careful 

 and repeated comparisons made between European and American 

 specimens of so-called B. cernua, I acknowledge inability to detect 

 any strong technical characters upon which to separate them." 



Again, in a single colony of B. cernua, frequently three or more 

 dissimilar forms occur, with numerous intergradations. Thus in a 

 single small colony north of Elgin, Illinois, many plants were 

 diminutive, matching B. minima Huds.; some were tall and 

 robust, matching B. Icptopoda Greene (the type of which Professor 

 J. M. Macoun of the Canadian Geol. Surv. Herb, at Ottawa kindly 

 permitted me to examine) ; and some were small plants grown from 

 the rooting nodes of tall plants trampled down by cattle, and were 

 practically identical with B. marginata Greene. In the same way, 

 several of Greene's types are found on comparison with their 

 cotypes in other herbaria to be merely slight variants from the 

 standard form. In several of these cases, Greene's description was 

 much too narrow to fit even the few cotypes examined. 



Bidens amplissima Greene, Pittonia 4:268. 1901. 



This species has been discussed already (Sherff, Bot. Gaz. 59: 

 312. 1915). The name Bidens elata then proposed as a substitute 

 has since been found, however, at variance with an example cited 

 in the Vienna Code for a similar case. Hence B. elata cannot be 

 retained as technically the valid name. 



Bidens laevis (L.) B.S.P. Prelim. Cat. 'N.Y. 29. 1888 — 

 Hclianthus laevis L. Sp. Plant. 906. 1753; Hclianthus joliis lancco- 

 latis scrratis laevibus Gronov. Fl. Virg. 1:104. I739; 9 Bidens chry- 

 saniliemoidcs Michx. Fl. Bor. Amer. 2:136. 1803; Bidens Iiclian- 

 thoides H.B.K. Nov. Gen. 4:230. 1820; Bidens clegans Greene, 



'I could not find Clayton's no. 195 among the Gronovian plants at the British 

 Museum, and am unable personally to confirm this citation except from Gronovius' 

 description. But, in r86o, Asa Gray (so Miss Mary A. Day of Gray Herbarium has 

 kindly ascertained for me) worked upon the Gronovian plants of the British Museum 

 and listed Clayton's no. 195 as " 195 Bidens chrysanthemoidesl (not Hdiopsis laevis)." 



