488 PROCEEDINGS OF THE AMERICAN ACADEMY. 
The retrorsely barbed bristles of this species, too, are slightly coarser than 
in the other plant, though for distinguishing the species this character is 
less to be relied upon than those found in the scales and tubercles. 
From Eleocharis palustris and £. olivacea this northern plant may 
generally be quickly separated by its annual habit, though, as noted in 
the Massapoag specimens, it very rarely produces late autumnal stolons. 
Its flexuous densely-clustered slender culms and its comparatively short 
ovate heads sufficiently distinguish it from the taller erect Z. palustris, 
with its narrower elongated heads. In habit the plant strongly suggests 
EL. olivacea (Figs. 23, 24), but in this latter perennial species the tubercle 
is narrower and lower, and of different outline: the sides, instead of being 
essentially straight, have a strong concave curve; and below, instead of 
rounding gradually to a slightly constricted base, the tubercle flares some- 
what like a saucer. 
Like Eleocharis intermedia and E. diandra, to which the northeastern 
plant has sometimes been referred, it is an annual. In habit it strongly 
suggests the former species, but that (Figs. 25, 26) has narrower spikes, 
and the more elongated achene is capped by a decidedly narrow deltoid 
conical tubercle reminding one of a very tall fool’s cap. Nor is the plant 
satisfactorily referred to Charles Wright’s obscure &. diandra. ¥. ge 
such specimens as we know (the original material) that species (Figs. 
53 to 58) seems to be of erect habit, and the narrower scales are pale 
brown with dark green midribs. The plant is unique in this group of 
annual species (excepting forms of the very different Engelmanni sec 
tion) in its entire lack of bristles; and its smaller obovate achene 18 
capped by a depressed tubercle about as broad and half as high as that 
of Mr. Hitchings’s plant, but in outline resembling a miniature tubercle 
of E. obtusa. In short, the northeastern plant, which has been referred 
at various times to the five species here discussed, is as distinct from all 
of them as are they from one another, and the only other described plant 
which seems to approach it is a form of Z. ovata of continental Europe 
Though Z. ovata is an erect plant, and has been so described by most 
European botanists, a single sheet in the herbarium of Dr. Charles W. 
Swan shows an extreme form collected by Seidel at Reichenbach 1 
Silesia, which is identical with the low flexuous-culmed plant first found 
in America by Mr. Hitchings. This depressed plant with flexuous culms 
hardly suggests to the casual observer the familiar erect Z. ovata, but it 
we certainly difficult if not impossible to find in their achenes any satisfac 
__ tory distinetions; and in northern Maine, at the single known station 
for the erect Z. ovata, there are puzzling specimens clearly intermediate 
