public boolean reserver(String rangee, int siege)
    {
    	String num = Place.getName(rangee, siege);
    	boolean libre = libres.containsKey(num) ;
        if (libre)
        {
        	Place place = libres.remove(num) ;
        	place.setLibre(false) ;
        	reservees.put(num,place) ;
        	informer();
        }
        return libre ;
    }