From Bot. Gaz. 56: 6: 494 in 1913:
Ker very justly separated this species from the smooth stemmed B. reptans (L.) G. Don. He laid too much stress however upon the indented ray of the latter species, this character varying too much to be of certain value. The recently described B. reptans tomentosa O.E.S. based on Geo. E. Nichols' no. 137, is merely a slightly smaller leaved form of B incisa L. G. Don, the terminal leaflets being less than "about two inches long." A study of several other collectors' specimens, notably at the New York Botanical Garden, some of which Dr Britton had already labeled Bidens incisa showed that the terminal leaflet varies in length from about 5 cm. to less than 3 cm. Some of the specimens examined were as follows: J.H. Hart (without date); Geo. E. Nichols 137, particularly the specimen in the Mo. Bot. Gard. Herb.; E.G. Britton, N.Y. Bot. Gard. Explor. Jam. 3867; N.L. Britton, same series 73.
Published in Hort. Brit. (Sweet), ed. 3.] 360 in 1839.