I do not have a photo of the interior (and can not even remember to have seen one) but as far as I know it is presumable that the cockpit framing was made of wood. This applies for Morane L (somewhere I saw a photo of the fuselage with canvas removed and the whole framing was wooden). As for Morane N, I do not see many reasons for metal tubing, as this is rather typical for german constructions. E. g. in England using metal tubes for airframe construction was not allowed until 1920's as the authorities did not trust the technology. I don't know how about France, but even significantly later constructions as for example the SPAD or Salmson were using wooden framing.
Sorry I can only support with best guess.
Ondra