STUDIES IN THE COMPOSITAE. 251 
4. Sketch of the History of BIDENS cERNUA, Linn. 
This is, typically at least, an Old World species; but it 
is commonly eredited with a very extensive distribution in 
North America, where it has hitherto been uniformly ac- 
credited as indigenous. That anything properly referable 
to B. cernua is native on our Continent I shall by and by 
call in question. But let me first give some of the older 
bibliography of the species. 
B. CERNUA, Linn. 
Bidens folio non dissecto, Cesalp. De Plantis, 488, (1583). 
Eupatorium cannabinum chrysanthemum, Tabern. Ic. 117 
(1590 
Cannabine aquatice similis capitulis nutantibus, C. Bauh. 
Prodr. 138 (1620). 
Cannabina acquatica folio non diviso, C. Bauh. Pinax, 
321 (1623). 
Bidens folio non dissecto, Tourn. Elem. 367 (1694) and 
Inst. 462 (1700). 
Eupatorium cannabinum chrysanthemum, Barrelier, Ic. 1209 
(1714). 
Ceratocephalus persica foliis, flore luteo radiato, Vaill. Mem. 
Acad. 326 (1720 
Bidens foliis longe ellipticis, serratis, indivisis, Haller, Helv. 
710 (1742) 
The above is a mere selection of the more important 
references to this plant by authors from Casalpinus down 
to the time when Linnzeus named it Bidens cernua, a period 
of about one hundred and seventy years. It was not until 
some time after Linnæus that any record was made of the 
occurrence of this species, or any cernuous Bidens at all, in 
America. In so far as I can ascertain, Willdenow, in 1803, 
