76 Rhodora [APRIL 
THE VALIDITY OF OXALIS AMERICANA. 
M. L. FERNALD. 
Tue Wood Sorrel of the northern mossy forests of eastern America 
has been known in all American writings since the days of Michaux 
and Pursh as Oxalis Acetosella L., thus implying the identity of our 
plant with the European species. Only at one period in American 
Systematic Botany has the identity of the American and European 
plants been questioned, and then only in a half-hearted way. In 1824, 
DeCandolle! published the American plant as Oxalis americana 
Bigelow in litt., separating it from the European plant, O. Acetosella, 
by its oblong unequally emarginate petals, as contrasted with the 
oval obtuse (not emarginate) petals of the European O. Acetosella. 
Bigelow himself in the same year (1824) treated the American plant 
as 0. Acetosella with the comment: “The American plant has the 
petals oblong and unequally bilobate, a character which might be 
considered specific, did not the European plant, as I find from.speci- 
mens, sometimes present the same figure.” ? Zuccarini, however, 
in his Monographie der amerikanischen Oxalis-Arten took up Bigelow’s 
O. americana,’ and again in his Nachtrag recognized O. americana as a 
distinct species. All subsequent authors, however, have followed 
Bigelow’s own printed statement and have not attempted to separate 
the American from the European plant. 
Our North American Wood Sorrel belongs distinctly in the Canadian 
zone, overlapping slightly into the Hudsonian, where it occurs in cool 
mossy woods, abounding through Canada from the southern side of 
the Labrador Peninsula to the Great Lake region, and south into 
northern New England and New York, and very locally at high eleva- 
tions or in cool mountain woods southward to the high mountains of 
North Carolina and Tennessee, and flowering in summer, from mid- 
June to August. O. Acetosella of Europe is a plant widely dispersed 
over the continent, running south quite to the Mediterranean region, 
and growing in apparently much drier open habitats, judging from 
1 DC. Prodr. i. 700 (1824). 
2 Bigel. Fl. Bost. ed. 2, 258 (1824). 
3 Zucc. Mon. am. Ox. 26 (1825). 
4 Zucc. Nachtr. Mon. am. Ox. 35 (1831). 
