1910] Fernald & Wiegand,— Arctium in North America 43 
A SYNOPSIS OF THE SPECIES OF ARCTIUM IN NORTH 
AMERICA. 
M. L. FERNALD and K. M. WIEGAND. 
For some time it has been apparent that the burdocks found in 
waste land in various parts of eastern America do not fall readily into 
the two or three catagories provided for them in our current manuals. 
Field observations during the past summer, and study of the accumu- 
lated material in the Gray Herbarium and the Herbarium of the New 
England Botanical Club, show that we have, established in America, 
four species which are commonly recognized by Old World botanists 
as growing in Europe. The peculiarities of the achenes, corollas, 
involucral bracts, and leaves, which are emphasized in European 
handbooks, so regularly accompany characteristic arrangements of 
the heads in the inflorescence, that upon the combination of these 
characters it is possible to classify all but the most immature material 
which has been examined. 
As judged from the conclusions of European authors, the species of 
this genus hybridize rather freely, and therefore in this country we 
should expect occasional more or less intermediate hybrid forms. But 
as yet so little attention has been given to the, genus in America that 
we are unable to state to what-extent our own plants hybridize. 
Plants with leaves somewhat laciniate or coarsely toothed have 
been reported from time to time as forms of A. Lappa, A. minus and 
A. tomentosum. One of the earliest records in America of such a 
variation was in Darlington’s Flora Cestrica (1837) where Darlington 
said: “A variety has been observed here, occasionally, with pinnatifid 
leaves" (p. 436). Specimens collected by Darlington have nonde- 
script inflorescences and on his label he states that “The inflorescence 
always has a kind of half-starved or semi-abortive appearance.” A 
similar form has recently been described in an unsigned note in The 
American Botanist (xv. 83, 1909) as A. minus f. laciniatum, in which 
the “inflorescence was irregular with numerous small sterile flowers.” 
The plants of this general character that we have seen have all the 
appearance of being teratological developments caused by some dis- 
turbing influence, and hardly merit special taxonomic treatment. 
On account of certain obvious characteristics of the burdocks most 
