Alismatidae
{{Short description|Subclass of flowering plants}}
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
[https://web.archive.org/web/20070927000050/http://www.accessscience.com/Encyclopedia/0/02/Est_022600_frameset.html?doi 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.