Exposing a pointer in Boost.Python

I have this very simple C++ class:

class Tree {
    public:
        Node *head;
};
BOOST_PYTHON_MODULE(myModule)
{

   class_<Tree>("Tree")
        .def_readwrite("head",&Tree::head)
    ;

}

I want to access the head variable from Python, but the message I see is:

No to_python (by-value) converter found for C++ type: Node*

From what I understand, this happens because Python is freaking out because it has no concept of pointers. How can I access the head variable from Python?

I understand I should use encapsulation, but I'm currently stuck with needing a non-encapsulation solution.