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
- superorder Alismatanae
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.