Trias stocksii

yes that would be a study worthwhile to do…
and why do some species of orchids prefer some tree?

Orchid seeds dont have endosperm of its own. So to germinate it needs help from a special group of fungi called mycorrhiza. These mycorrhiza are very much habitat specific too. If you remember some basics of
fungi then you will know that fungi are highly specific a simple example is that the wheat rust fungi will not cause rust in rice.
These mycorrhiza are very much specific where they grow. They are even specific to the moisture content. For a tree if you look at the trunk skeleton, humidity increases as you go to bottom from top of a tree (on the trunk). Hence the ultimate branches are driest where as the main trunk are most moist. Hence mycorrhizal community also differs along the height on the tree trunk. On the other hand when you look at orchids, some are generalists, as they can grow anywhere, i.e. may be they can get associated with any mycorrhiza. But there are specialists which grow exclusively with some particular mycorrhiza. For example, orchids like Aerides multiflora, Aerides odorata, Vanda tessellata etc are generalists and they can grow on many host trees and all parts of the host. But orchids like Oberonia, some of its species are referred to as twig epiphytes. They grow on the ultimate branches of particular host trees. These phenomena can also been seen on the ground orchids.
Corallorhiza trifida grows near Betula trees on ground.
Hope this answers your question.
But this area is still under-studied and hence needs some attention to come out with some better conservation measures for these valuable plants.
There is also a theory that almost all plants of the world, at some point of their life history needs a contact of some fungi.

yes thank you, truly… it answers the curiosity for a while…
but if I sit down to ask really scientifically tough question it would take a lot of time and may be bore the other members…
being a physician, I learnt to look at fungi as opportunistic infectious agents… that if given a chance would kill.like the aspergilous in lung or brain or histoplasmosis … etc.. and then there is candida.. a boon to the modern drug industry… we are always primed to kill fungi as soon as we see them…
BUT
but trying to sprout banana seeds in my cold nyc apt I needed to wait till some airborne fungi took pity on my seeds in the bottle on a wet gauze and coated them with their slimy growth , and then my seeds sprouted… I developed a sort of fondness for them…