Do AssetBundles retain directory path names?

If I create an asset bundle from a whole directory of items, are the original paths kept in the bundle, or is everything flattened? All of the documentation and samples for loading assets are very simplistic and don't mention this at all.

For example, I want to do the following:

obj.mesh = assetBundle.Load("Scene01/Meshes/mesh.asset", typeof(Mesh)) as Mesh;

But this doesn't work. It returns null. I've tried variations of the path and removing the file extension, but get nothing.

try: obj.mesh = assetBundle.Load("Assets/Scene01/Meshes/mesh.asset", typeof(Mesh)) as Mesh;