1914] Fernald & Long,— Variations of Potentilla palustris 5 
lists may be due to this cause; in this case it is only because the “ con- 
signment" came ashore at a point itself barren that the detection 
and correction is so easy; if it had been at a place where deep water 
plants from just off shore were also coming in, it might be quite per- 
plexing. It may seem like severity to put all deep water plants on 
the waiting list until some dredging expedition vouches for their 
eligibility, but it may be the only safe way. 
Norra EASTHAM, MASSACHUSETTS. 
THE AMERICAN VARIATIONS OF POTENTILLA 
PALUSTRIS. 
M. L. FERNALD AND Bayarp Lona. 
(Plate 106). 
In 1908 attention was called by Dr. Theodor Wolf,! in his Mono- 
graphie der Gattung Potentilla, to the fact that in North America 
Potentilla palustris is not a uniform species but that the little known 
var. villosa (Pers.) Lehm., a plant of rare occurrence in northern 
Europe and possibly Greenland, is also found on the continent of North 
America (Cartwright, Manitoba). In 1909 our knowledge of var. 
villosa was sufficient to justify the statement that it is found “ Through- 
out the St. Lawrence system from n. N. S. and e. Que. to L. Superior 
and L. Winnipeg,"? and in 1910 the plant was recorded as “the 
common form of the species in eastern Washington County, Maine." ? 
In the study of this and other variants of P. palustris it has been 
necessary to look with some detail into the plant throughout its known 
range and into the very different treatments of its variations by au- 
thors, either as a Potentilla or as a separate genus, Comarum. As a 
result of these studies it seems to the writers that the plant in America 
falls into three well marked varieties with pronounced geographic 
ranges. 
1 Wolf. Mon. Pot. 76 (1908). 
2 Robinson & Fernald, Ruopona, xi. 48 (1909). 
3 Fernald & Wiegand, Ruopora, xii. 140 (1910). 
