Below is some rare footage of a tree octopus from 1928:

The scenes were shot by the French experimental filmmaker Jean Painlevé and originally appeared in his surrealist nature film about octopuses, La Pieuvre (The Octopus). The silent short with the scenes in their original context can be found in the recently released Criterion Collection of Painlevé's work, "Science Is Fiction: 23 Films by Jean Painlevé".

(Thanks to Joshua for bringing this to my attention.)