This plant from the Brazilian Pantanal region was first considered to be a Hygrophila species, however, the characteristics of its inflorescence put it in the coffee family (Rubiaceae), and it is very probable that it belongs to the species Diodia kuntzei.
In the USA, Diodia cf. kuntzei has gained some popularity as aquarium plant under the name "Hygrophila sp. 'Pantanal' ". It is probably not yet cultivated in Europe.
-To be continued-
<a href="http://www.flowgrow.de/db/aquaticplants/diodia-cf-kuntzei" target="_blank"><img alt="Diodia cf. kuntzei" title="Diodia cf. kuntzei" src="http://www.flowgrow.de/db/widget/aquaticplants/diodia-cf-kuntzei" /></a>
[widget=aquaticplants/diodia-cf-kuntzei]Diodia cf. kuntzei[/widget]