240 Rhodora [DECEMBER 
being trigonous, while those of the American S. rbbustus are com- 
pressed or lenticular. ‘The achenial character seems a constant one 
in the American plants examined ; and this, together with the thicker 
spike already emphasized by Michaux and Pursh who must have 
been familiar with the true S. maritimus of Europe, sufficiently dis- 
tinguishes S. robustus of Pursh from the Linnean species with which 
it has been confused. Some specimens from our Pacific coast are 
doubtfully referred by Dr. Britton to the true S. maritimus, but no 
mature achenes have been examined, and for the present the status 
of that species in our flora must remain doubtful, 
In the Illustrated Flora Dr. Britton describes as A. robustus the 
plant with spikelets “in a dense, often compound, terminal clus- 
ter." . This, as already stated, is the commoner form of the plant on 
our northeastern coast, but the form obviously intended in the de- 
scriptions of both Michaux and Pursh is the one with definitely 
branching inflorescence. In the same work Dr. Britton describes as 
a species, S. campestris, a rather characteristic plant of the Great 
Plains and Rocky Mountains, with exceedingly light-colored spikelets. 
Except for the rather inconstant color character, this Great Plain 
plant does not differ, however, from the dense-headed plant of the 
coastal region. 
In 1899 Professor Aven Nelson published as a species, Scirpus 
paludosus, a Wyoming plant similar to S. campestris, Britton, “from 
which it is clearly separated by its remarkable tubers ( subspherical, 
10-25 mm. in diameter)," as well as by its darker scales and achenes. 
Comparison with specimens from Professor Nelson shows that his 
species is in no way different from the common American plant with 
brown spikelets in dense terminal heads. Furthermore, A, PaZudosus 
instead of differing from S. campestris in its “ remarkable tubers” is 
very like that plant (as shown by herbarium specimens ) in this point— 
a character likewise shared by the European S. maritimus as well as 
our own S. robustus. 
In his description of Scirpus campestris, Dr. Britton emphasized 
the pale color of the achenes, but an examination of mature achenes 
shows them often to be quite as dark as in A. ^a/udosus and the larger SS. 
robustus. With only the pale color of its spikelets to ‘distinguish it 
from the common dense-headed form of S. robustus, S. campestris seems 
much better treated as a Great Plain variety of that species. The 
identity of Nelson's A. paludosus and the common form with congested 
