248 PITTONIA. 
described as flore luteo. It is a fact, after all, very 
seriously to be considered, that when the predestined B. 
frondosa first appeared in European botanic gardens, and 
while as yet no other plant but the native B. tripartita was 
there with which to compare it, the American one was de- 
scribed as yellow-flowered, while the native one had never 
been so designated. Of course, the Bidens “flower,” with 
not only the earlier authors, but with Linnsus as well, was 
the head, including the double involuere, the outer mem- 
ber of which was called the calyx. Now B. melanocarpa of 
Mr. Wiegand is admitted to exhibit yellow rays, and those 
quite copiously at earliest flowering; and I have often ob- 
served that all through its flowering period, even when ray- 
less, the bracts of the inner involucre almost glow with a 
coppery or brownish yellow. But B. tripartita is rayless, 
and its involueres are said to be of a dark, reddish brown. 
It would not, therefore, have been described as flore luteo. 
No more would my B. vulgata have been so designated, for 
its involucres are green, it has no rays, and even its disk- 
corollas are only “pale-yellow,” as Mr. Wiegand himself 
says, in describing it as * B. frondosa." 
Again: it was owing to the yellow eoloring of the heads— 
yellowish as to involucre, yellow as to small rays and deep- 
yellow disk—that the predestined B. frondosa was early 
transferred to Chrysanthemum, a fate which did not befall 
the rayless B. tripartita until much later, and after it had 
been realized that all of them, radiate or rayless, belonged 
in the same genus, and natural conservatism prevented 
either the establishment of a new genus or the restoring of 
the then long forgotten Bidens. 
It is in Morison's Plantarum Historia Oxoniensis that one 
meets with the earliest full and satisfactory descriptions of 
species of Bidens. They are still so few—only five in all— 
