250 Rhodora [OcTOBER 
available American and European material has brought out a number 
of interesting points in regard to the group of annual species of which 
Scirpus supinus, L., may be taken as the type. This small group of 
species is characterized by annual roots, rather slender essentially 
naked culms and few (rarely solitary) sessile spikelets much over- 
topped by the elongated involucral leaf. The species are super- 
ficially very similar, but in the achenes and their subtending scales 
they show certain very constant differences. 
'The presence or absence of a perianth of bristles, which has long 
been considered an important character, does not seem, however, a 
point sufficiently constant for specific diagnoses. Plants with other- 
wise identical characters, and differing only in the presence or absence 
of the bristles are well known in other genera of the Cyperaceae. 
Among such cases are E/eocharis Englemanni and its var. detonsa, 
and Æ. palustris, and its var. cava ; while in Fleocharis monticola, 
var. viseta, and Rhyachospora capillacea, var. leviseta, the reduced 
bristles lack the barbellate character found in the otherwise undistin- 
guishable species. It is not, then, very surprising to find that the 
extensive area of Scirpus debilis at Massapoag Lake quite lacks the 
characteristic perianth of the species, thus exhibiting a tendency par- 
allel with that found in species of related genera. 
The other species of the group are described as lacking the peri- 
anth, or in case of Scirpus Smithii as having “bristles 1 or 2 minute 
rudiments or none." A study of the material in the Gray Herbarium 
shows, however, two sheets of specimens collected by S. B. Mead in 
Illinois, in 1845, in which the spikelets and the achenes are undoubt- 
edly of S. Smthii, but the bristles are as elongated and retrorsely 
barbed as in typical S, debilis. The European S. supinus ordinarily 
quite lacks a perianth, yet one specimen from Versailles distinctly 
shows rudimentary bristles, while similar rudiments are occasionally 
seen in its better known American representative, S. ZZa//i. In view 
of these facts it is apparent that we can no longer rely for final spe- 
cific distinctions upon the presence or absence of bristles in this 
group; and that the characterizations of the species as now treated 
in our manuals must be considerably modified. Study of all the 
material at hand shows that in the achenes themselves we find 
characters of such constancy as to furnish a much safer basis for 
classification. The color of the achenes in all the species is very 
variable, but the shape and deeper markings supply the characters 
upon which is based the following synopsis. 
