Alismatidae
# Alismatidae

Alismatidae 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 system

The Takhtajan system treats this as one of six subclasses within the class Liliopsida (=monocotyledons). It consists of:

* subclass Alismatidae

    superorder Alismatanae
       order Butomales
       order Hydrocharitales
       order Najadales
       order Alismatales
       order Aponogetonales
       order Juncaginales
       order Potamogetonales
       order Posidoniales
       order Cymodoceales
       order Zosterales

## Alismatidae in the Cronquist system

The Cronquist system treats this as one of four subclasses within the class Liliopsida (=monocotyledons). It consists of (1981):

* subclass Alismatidae

    order Alismatales
    order Hydrocharitales
    order Najadales
    order Triuridales

This subclass comprises less than five hundred species total: many of these are aquatic or semiaquatic plants (see Alismatidae info).

## APG II system

The 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.

