1917] Fernald,—Circaea canadensis and C. intermedia 85 
THE IDENTITY OF CIRCAEA CANADENSIS AND 
C. INTERMEDIA. 
M. L. FERNALD. 
In 1915 the present writer pointed out ! that the Alleghanian plant 
which has long passed in America as Circaea lutetiana L. is not that 
species, but is rather C. latifolia Hill, Brit. Herb. 138 (1756). At 
that time he did not enter into a discussion of the other species of 
Circaea in eastern America, wishing to make further studies of the 
plants before pronouncing upon their identities. 
Besides the common C. latifolia of deciduous woods from western 
New Brunswick westward and southward, we have the more northern 
C. alpina L. which differs in very many characters from C. latifolia, and 
a third plant somewhat intermediate both in size and technical char- 
acters between the two, the plant which is passing in our manuals as 
C. intermedia Ehrh. Beitr. iv. 42 (1789). That this third plant is iden- 
tical with the European C. intermedia there seems little question, sev- 
eral sheets of European specimens showing no characters by which the 
American and European material can be separated. This plant, which 
is related to C. latifolia and to C. lutetiana in having the fruit 2-celled 
(as contrasted with the 1-celled fruit of C. alpina), and the root-stock 
slender (as contrasted with the tuberous-thickened root-stock of C. 
alpina) and comparatively large flowers, differs at the same time from 
C. latifolia in several definite characters. Its stems are comparatively 
weak and succulent; the leaves pale green and flaccid, as in C. alpina, 
broadly ovate and usually cordate, with very prominent sharp denta- 
tion; the petiole channeled or distinctly margined; the fruiting pedi- 
cels merely spreading or only slightly deflexed; the disk inconspicuous 
and not prolonged (as contrasted with the definitely prolonged cup- 
like disk of C. latifolia); and the mature fruit 1.5-3 mm. thick, includ- 
ing the long soft trichomes, and not corrugated (as contrasted with the 
strongly corrugated fruits of C. latifolia which are 3.5-5 mm. thick, 
including the strongly hooked bristles). 
That the three species are perfectly distinct there can be no question, 
although in Europe C. intermedia has sometimes been considered a 
1 Ruopora, xvii. 222 (1915). 
