  We analyse the existence question for essential laminations in 3-manifolds.
The purpose is to prove that there are infinitely many closed hyperbolic
3-manifolds which do not admit essential laminations. This answers in the
negative a question posed by Gabai and Oertel. The proof is obtained by
analysing certain group actions on trees and showing that certain 3-manifold
groups only have trivial actions on trees. In general the trees are neither
simplicial nor metric. There are corollaries concerning the existence question
for Reebless foliations and pseudo-Anosov flows.
