azolla microphylla, azolla nilotica or azolla anabaena or water fern or azolla filiculoides or water lettuce ,stemless water plant

filiculoides oligorrhiza anabaena terminalia hydrophytic craib cool lemma day droplet hydrophyte dew polyrrhiza leaf rain fern schleid bud seasonal stemless nilotica lettuce flower well lemnaceae plant lotus combretaceae glaucifoloa cold pistia lemna aquatic season water wet spirodela minor stratiotes perpusilla pond drop azolla lesser rainy microphylla river genus duckweed