AlismatidaeAlismatidae is a botanical name at the rank of subclass. Circumscription of the subclass will vary with the taxonomic system being used (there are many such systems); the only requirement being that it includes the family Alismataceae. It is a relatively new name: earlier systems, such as the Engler and Wettstein systems, used the name Helobiae for a comparable unit.
Alismatidae in the Takhtajan systemThe Takhtajan system treats this as one of six subclasses within the class Liliopsida (=monocotyledons). It consists of:
Alismatidae in the Cronquist systemThe Cronquist system treats this as one of four subclasses within the class Liliopsida (=monocotyledons). It consists of (1981):
This subclass comprises less than five hundred species total: many of these are aquatic or semiaquatic plants (see [https://web.archive.org/web/20070927000050/http://www.accessscience.com/Encyclopedia/0/02/Est_022600_frameset.html?doi Alismatidae info]).
APG II systemThe APG II system does not use formal botanical names above the rank of order; it assigns most of the plants involved to the (expanded) order Alismatales, in the clade 'monocots', although the plants in Cronquist's order Triuridales are assigned to quite different placements.