I went back and read a set of UBC posts that I made last year with others on this forum trying to figure out the difference in Philodendron martianum and Philodendron cannifolium. The bottom line, at least as far as science goes, is the correct name is Philodendron martianum and on three different occasions the name Philodendron cannifolium has been declared invalid in science for various reasons including the fact the name was used for a plant from a completely different genus. The confusion of the names originated with Dr. von Martius for whom the original published drawing named "Philodendron cannifolium" was made. He used the wrong name in a book he published in the 1800's. and his name stuck with horticulturists. Later scientists named the plant in his honor calling it Philodendron martianum. The two names are not scientific synonyms. This is a very long story and somewhat confusing but with the help of several scientific minds we managed to work out the details which you can read here: http://www.exoticrainforest.com/Philodendron martianum pc.html
I have seen this sp. growing in very bright light here in the wet tropics . Foliage was nearly yellow and quite small . I actually thought it was some strange orchid [ this was over 20 years ago ] Have not seen much around lately . But a mate got a tray of T/C plants with printed tag . Philo. martianum x cannifolium !!!!
Interesting Mic. Marcus Nadruz in Rio says P. martianum normally is an epiphyte but if the tree falls the plant grows much larger in the ground. I included a photo on my page of Leland Miyano's plant which is very large but also planted terrestrially. The name confusion is likely going to continue forever.