This name is a synonym of Alisma gramineum Lej..
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 274723) with original publication details: Amer. Midl. Naturalist 58: 487 1957.
This name record (from WCSP) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Alisma gramineum in version 1 of The Plant List.