ALISMATACEAE

CLXX. ALISMATACEAE View in CoL View at ENA 1

Aquatic or marsh herbs, usually perennial. Leaves alternate or basal, sheathing at the base. Flowers hermaphrodite orunisexual, usually bracteate and verticillate in pedunculate umbels, racemes or panicles, occasionally long-pedunculate in leaf-axils. Sepals 3. Petals 3, usually larger than the sepals, often fugacious or deciduous. Stamens 3-numerous, with elongated filaments; anthers opening by longitudinal slits. Carpels 3-numerous, spirally arranged or whorled, free or 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.

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; these leaves are not mentioned in the keys and descriptions unless they are characteristic of mature flowering plants. When growing in relatively dry habitats the plants are usually dwarfed and may be misleadingly different from plants growing in wetter conditions. 1 Flowers unisexual; stamens 7-numerous 1. Sagittaria 1 Flowers hermaphrodite; stamens 6

2 Carpelsconnateatthebase ina singlewhorl,2 -tomanyovulate, follicular and stellately radiating in fruit, ± long-beaked 6. Damasonium 2 Carpelsfree,1-ovulate,achenialordrupaceousinfruit, short-beaked

3 Carpelsnumerous, spirallyarrangedina globosehead; flowers in simple inflorescences of 1-3 whorls, or long-pedunculate in leaf-axils 2. Baldellia 3 Carpelsfew ornumerousina single,sometimesirregular whorl

4 Stems elongated, rising in the water and bearing floating leaves or creeping and rooting at the nodes; flowers pedunculate in leaf-axils; carpels 6-15 in an irregular whorl, with apical styles; fruitlets many-ribbed

3. Luronium 4 Stems short, the leaves all basal; flowers in panicles, racemes or umbels; carpels in a regular whorl, with subventral styles; fruitlets 3- to 5-ribbed or unribbed

5 Carpels 5-10; fruitlets drupaceous, swollen, with woody endocarp and spongy exocarp; leaves deeply cordate to subcordate 5. Caldesia 5 Carpels 11-28; fruitlets achenial, laterally compressed;

leaves not deeply cordate 4. Alisma