1889.] NEW-YORK MICROSCOPICAL SOCIETY. 95 



THE GENUS ELEOCHARIS IN NORTH AMERICA. 



BY N. L. BRITTON. 

 {Read October \%th, 1889.) 



The Cyperaceous genus Eleocharis was proposed by Robert 

 Brown in iSio, in his famous " Prodromus Florce Nova Hol- 

 landite," where several Australasian species are first described 

 and a large number of others, formerly known as Scirpi, are 

 stated to belong to the new genus. Since that time it has been 

 very generally accepted by systematic botanists as distinct from 

 Scirpus, although Dr. Asa Gray appears to have been in some 

 hesitation concerning this for he has described one species as 

 Scirpus {Eleocharis) Wolfii. While otherwise closely allied it is 

 here maintained that all the species may at once be known from 

 the unispicate Scirpi, by the style-base forming a persistent 

 tubercle, not confluent with the body of the achene, as it is in 

 the otherwise nearly related species of that genus. 



The American forms have not been critically studied since 

 1836, when Dr. Torrey's monograph on North American 

 Cyperacere was published, in the 3rd volume of the Annals of 

 the New York Lyceum of Natural History. Nineteen species 

 of Eleocharis are there recognized, including one now referred 

 to Scirpus {E, pygmcea, Torr.). Seven of these nineteen were 

 described as new and six of them have stood the test of 53 

 years' study. To these 18 species of Torrey we may now add 

 22, for I find that I can individualize 40 as North American. 

 Of these, four only have not yet been collected in the 

 United States, one of them {E. geniculata) not coming north of 

 S. Mexico so far as I am informed, the others extending to 

 Central Mexico. The United States may thus claim 36 species, 

 or double the number known to Dr. Torrey in 1836. 



The morphology of the genus may be thus summarized : The 

 roots are either fibrous and annual or they are accompanied by 

 perennial rootstocks and thus serve as characters in grouping 

 species ; the stems are simple columns, ranging from less than 

 an inch to nearly three feet in height and in section they are 

 terete, wing-angled, nodose or flattened ; the leaves are rep- 

 resented only by sheaths or vaginoe, which terminate at their 

 orifices in short teeth, in a truncate border, or in some sharply 

 defined species in scarious spreading borders ; the stems are 



