Arboreal aliens on a tropical rain forest world. They have a flower-like chest organ with which they communicate and/or feed from trees. Concept of "gamish"..a life force.
Not sure if story also depicts technological imperialism, a la Avatar, but it may.
This review of Eric Frank Russell's Symbiotica provides a quote from the story about trees, alien chest organs, and life-giving fluids.
"The communal point is that queer chest organ... there are some higher than the Ka, higher than all others, some so high and godlike that they could depart from their trees and travel the globe by day or by night. They could milk their trees, transport the life giving fluids and absorb them from bowls. Of the symbiotic partnership imposed upon them, they had gained the mastery and - in the estimation of the planet - they alone were free."
Also a mention of gamish:
"Kala of the tribe of Ka. All members of his group are named Ka-something... every man has his tree... I don't understand what he means by that, but he satisfied me that in some mysterious manner his life depended upon him being with his tree during darkness. It was imperative. I tried to delay him but his need was pitiful. He preferred to die rather than be away from his tree... We also learned that there are others in the dark, others mightier than the Ka. They have much gamish... anything unusual or surprising or unique is chockful of gamish. Anything merely abnormal has a lesser amount of gamish. Anything ordinary has none whatever."
