It found it blooming in Rio de Janeiro town in February 2010
Thank you!

My guess is Pseuderanthemum reticulatum.

Pseuderanthemum reticulatum it is!
Thank you Danita!

I would first check that this is not a synonym of any of the species listed for Brazil Myriam, here's the list for Brazil..


Acanthaceae Pseuderanthemum bolivianum Britton ex Rusby
Acanthaceae Pseuderanthemum congestum (S.Moore) Wassh.
Acanthaceae Pseuderanthemum detruncatum (Nees ex Mart.) Radlk.
Acanthaceae Pseuderanthemum exaequatum (Nees) Radlk.
Acanthaceae Pseuderanthemum heterophyllum (Nees) Radlk.
Acanthaceae Pseuderanthemum leptostachyum (Nees) Radlk.
Acanthaceae Pseuderanthemum macrophylum (Nees) Radlk.
Acanthaceae Pseuderanthemum modestum (Nees) Radlk.
Acanthaceae Pseuderanthemum riedelianum (Nees) Radlk.
Acanthaceae Pseuderanthemum verbenaceum (Nees & Mart.) Radlk.


A perhpas true photo of Pseuderanthemum reticulatum

http://en.wikipedia.org/wiki/P...

Thanks Janet to warn me to be cautious with the specie name!
The picture on Wiki of Pseuderanthemum reticulatum looks a bit different, and probably is more reliable that the pics I found..I have googled all the others from the list you gave, but many have no images available..
Better keep it to Pseuderanthemum sp.!