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 pnlustris and E. olwacea 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 Ji!. palustris, 

 with its narrower elongated heads. In habit the plant strongly suggests 

 E. 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, 20) 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 E. diandra. From 

 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 unicpie in tliis group of 

 annual species (excepting forms of the very different Engelmanni sec- 

 tion) in its entire lack of bristles; and its smaller obovate achene is 

 capped by a depressed tubercle about as broad and half as high as that 

 of Mr. Ilitchings'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 E. ovata of continental Europe. 



Though E. ovata is an erect plant, and has been so described by most 

 European botanists, a single sheet in the herbarium of Dr. Charles "\V. 

 Swan shows an extreme form collected by Seidel at Reichenbach in 

 Silesia, which is identical with the low flexuous-culmed plant first found 

 in America by Mr. Ilitchings. This depressed plant with flexuous culms 

 hardly suggests to the casual observer the familiar erect E. ovata, but it 

 is certainly difficult if not impossible to find in their achenes any satisfac- 

 tory distinctions ; and in northern Maine, at the single known station 

 for the erect E. ovata, there are puzzling specimens clearly intermediate 



