Me Ee RRS on C 
1918] Fernald,— Bidens hyperborea and B. colpophila 147 
regards, but that the Maine coast B. colpophila is certainly conspecific 
with B. hyperborea. With these decisions of Dr. Sherff the writer is 
entirely in accord but a detailed study of all the material has con- 
vinced him that, although the Gaspé plant differs in certain habital 
traits, it, with all the other variations, from James Bay, the Maine 
coast and the lower Merrimac, makes up a single species with certain 
very clearly marked characters. The superficial trait which separates 
this complex species of the estuaries and saline marshes, B. hyperborea, 
from the B. cernua, with which it is most apt to be confused, is the 
erect heads which commonly remain quite erect in fruiting, B. cernua 
when well developed having the fruiting heads abruptly nodding. In 
B. hyperborea and its varieties the outer involucre consists of strongly 
ascending or only slightly spreading bracts; the outer involucre of 
B. cernua being reflexed or strongly divergent, not ascending. The 
disk-corollas of B. hyperborea are 4-toothed, of B. cernua commonly 
5-toothed. In B. hyperborea the anthers are included, becoming 
exserted only by the shriveling of the corolla; in B. cernua the anthers 
are commonly exserted and conspicuous in the fresh flowering material. 
But the greatest difference between the two species is in the achenes. 
In B. cernua the fully matured achene is curved and with almost wing- 
like coarsely retrorse-barbed pale margins and keels and its surfaces 
between the keels and margins ordinarily smooth or only obscurely 
furrowed; the outer achenes are 3.3-6.3 mm. long and 2-2.8 mm. 
wide; and the central achenes 4.2-7.8 mm. long and 1.8-2.5 mm. wide. 
In B. hyperborea, on the other hand, the achenes are straight, flat or 
flattish and not wing-margined nor with prominent keels, only slightly 
thickened at the summit and with 7-15 prominent ribs on each face; 
and the outer are 4.2-8.4 mm. long, the inner 6-10 mm. long, 1.4-1.9 
mm. broad, i. e. the achene is flat and more slender than in B. cernua. 
That B. hyperborea (including B. colpophila) is thoroughly distinct 
from B. cernua there can be no question, but the species is itself highly 
variable, the varieties apparently being very definitely isolated. The 
typical plant from James Bay is not exactly matched by any material 
the writer has seen, although it is very close to some of the Maine 
1 Some dried material collected by the present writer shows arching of the peduncles which 
gives in the herbarium the impression that the heads are sometimes nodding; but in these 
cases the arching was due to leaving the specimens over night in the collecting boxes, and their 
consequent bending toward the light entering the boxes in the early morning. All material 
in the field, where the present writer is very familiar with the plant, shows quite definitely 
ascending fruiting heads. 
s Ne 
