Recursive Random Selection of a Node inside a Tree

I've developed a recursive algorithm in c++ to select a random node inside a Tree (not necessarily binary). This is the code:

    Tree* Tree::SelectRandomNode()
    {

    static int n = 0;
    static int selected;

    Tree *Ret;

    n++;

    // If It is a Terminal Node, it chooses a random node between those we got through
    if( !InnerNode ) selected = rand()%n;

    // Else if it is an Inner Node, it keeps going through random children
    else Ret = Child[ rand()%NumberOfChildren ]->SelectRandomNode();

    n--;

    //Then, when we get back, we take the pointer of the selected node
    if( n == selected ) return this;
    else return ret;

    }

What do you think about it? Is it efficient? Then, for curiosity, is this an O(log(n)) algorithm? There are faster ways to achieve this?

PS: I know very little about computational complexity.