What is the name of the plants that grow on trees?
There are a lot of things that grow on trees. You'll find Spanish moss growing and hanging on trees. You'll also find wild ferns and many other things. If you go to http://bit.ly/el1tSd you'll see all sorts of things growing on trees.
Do you mean a generic word for such plants? If so, the are called epiphytes.
I don't think there is one specific name but many (more than 10).
In Florida we have the ubiquitous air plant.
Well the plants on the trees it could be Poison Ive Poison Oak or even Sumac. It depends of what the leaf looks like.