I found them growing sometimes in very dark spots in the forest.
At first sight it looks a bit like a Pachystachys, but the actual flowers don't match.

Acanthaceae seems to be the right family, I found Aphelandra maculata which comes close but not close enough ..

http://plantillustrations.org/...

http://idtools.fieldmuseum.org...

Aphelandra prismatica is closer..

http://www.brazilplants.com/ac...

http://www.brazilplants.com/ac...

http://www.brazilplants.com/ac...

http://plantillustrations.org/...

https://www.flickr.com/photos/...

It's in Rio de Janeiro ..

http://reflora.jbrj.gov.br/jab...

Thank you Janet! I do think that Aphelandra prismatica probably is the plant, though I don't remember having seen the whitish spot in the throat of the flower like in the plant on Brazil.com but that seems to be is a cultivar: 'Poço das Antas' so that could explain it.
I don't think it could be anything else..
http://www.brazilplants.com/ac...
It is strange there is so little photo material of the plant on the web..
I had been searching in the Acanthaceae family earlier as it looked so close to the well-known Pachystychas but didn't find anything matching!

Brazilplants.com site might certainly be useful for others, I still have piles to ID!

I should have gone to the Brazil plants for a start Myriam, I did think about it but didn't think he would be selling seeds of such a plant! I think I found another Aphelandra sp. on FloraSBS with similar shaped flowers but it was blue, a search brought me to the plantillustrations site. A long route after looking at other sites!

Mauro does list the location from which he collects seed, the differences suggest the species is variable.

I know Janet, the routes to get to the right plant can be very long and time consuming, but mine was fruitless and frustrating!
We are so lucky to have you here!

I see that Mauro gives cultivar names on plants found in the wild like mine.
I thought a cultivar name is only given to plants that involves human intervention, like careful breeding and selection?
Should those wild plants not get a variety name instead?

I don't think the names which Mauro give are cultivar names Myriam, they seem to be only locations to reflect where he got the seed from which, in many cases, also shows species variation due to location. They are still the same species.

I see Janet, that makes sense!