Look, up in the tree! What is that wierd stuff?

What is that up in the tree? (Courtesy of Paula Richards)
What is that up in the tree?
(Courtesy of Paula Richards)

Looking up into an oak tree, we spotted some interesting fuzzy plants that seemed to be growing in clumps along the branches.  They do not have roots that reach to the ground.  How do they get water and nutrients?  Do you think it’s harmful to the tree?  What kind of plant is this?  Can you think of other plants that grow in a similar fashion?

Answers found at this link.