General Description:- Aquatic or marsh herbs, usually perennial.
Leaves:- Alternate or basal, sheathing at the base.
Flowers:- hermaphrodite or unisexual, usually with bracts (bracteate) and arranged in whorls (verticillate) in stalked (pedunculate) umbels, racemes or panicles, occasionally long-pedunculate in leaf-axils. Sepals 3. Petals 3, usually larger than the sepals, often falIing off early (fugacious) or deciduous. Stamens 3-numerous, with elongated filaments; anthers opening by longitudinal slits. Carpels 3-numerous, spirally arranged or whorled, free or joined (connate) at the base; ovules 1-many; styles apical or subventral.
Fruit:- A group of achenes, drupelets or follicles; seeds without endosperm; embryo horseshoe-shaped.
Genus:- ALISMA
Leaves:- Aerial, floating or submerged.
Flowers:- Hermaphrodite, in panicles or occasionally (in small plants) in racemes or umbels. Stamens 6. Carpels numerous (11-28) in a single whorl, free, each with 1 ovule; styles subventral.
Fruit:- Fruitlets achenial, laterally compressed, obovate to elliptical, with a short ventral beak.
Key feature:-
1) Carpels 11-28.
2) Fruitlets achenial, laterally compressed.
3) Leaves not deeply cordate.
Comments:-
All European species of this family grow in marshes or in shallow water at the edges of lakes, ponds, canals or slow rivers. Most of them, when growing in water, can produce linear, phyllodal submerged leaves which may or may not persist. When growing in relatively dry habitats the plants are usually dwarfed and may be misleadingly different from plants growing in wetter conditions.