1918] Fernald,— Validity of Oxalis americana 77 
photographs which show O. Acetosella associated in colonies with 
Anemone nemorosa and other plants of open woods; and in Europe 
the plant flowers in early spring, mostly in April and early May. 
Thus it would seem that O. Acetosella of Europe is one of the early 
spring flowers of open sunny woods, while its North American repre- 
sentative is a summer-flowering plant of the dense Canadian spruce 
and fir forests. This discrepancy in the flowering seasons and the 
ranges of the plants at once suggests that they are probably not con- 
specific, since most plants of Canadian distribution in America occur, 
when they are found in Europe, much farther north than with us. 
The examination of very many plates, in fact all the plates found 
of the European species, shows the petals to be represented always as 
obovate and entire, or merely undulate or very obscurely notched at 
summit; the American material having, as Bigelow said, oblong petals 
with a conspicuously oblique notch at the tip. Some herbarium 
material of the European plant, poorly dried, appears, apparently by 
shrinkage, to be slightly emarginate, but it is significant that the 
European plates are so constant in showing scarcely any notching. 
Other characters appear upon investigation. For instance, the cap- 
sule produced from the petaliferous flowers in the European plant is 
conic-ovoid, this form showing not only in herbarium material but 
in all the excellent European plates; the capsule from the petaliferous 
flowers of the American plant, on the contrary, is depressed-globose, 
barely tapering at summit and in some cases almost oblate. The 
seed of the European plant is conspicuously ribbed with acutish 
parallel ridges, but the seed of the American plant has these ridges 
nearly or quite obsolete, the surfaces being smooth or only obscurely 
ridged. The sepals of the European plant have very delicate margi- 
nal hairs, which are usually appressed to the margin and not readily 
seen, while the sepals of the American plant are conspicuously hispid- 
to villous-ciliate with widely spreading reddish hairs. Another char- 
acter of fair constancy appears in the rootstock. In the American 
plant the persistent bases of the old petioles are conspicuous on the 
rootstocks on account of the circular calloused tip (the point of 
disarticulation of the old petioles); in the European material and in 
the European plates these calloused tips are rarely seen, this difference 
arising from the fact that in the American plant the disarticulation of 
the petiole takes place above the tips of the subtending persistent 
stipules, in the European well below the tips of the stipules. 
