undefined reference to 有关问题

//Tree.h 
 1 #include<iostream>
  2 using namespace std; 
 10 template < typename T>
 11 struct node{
 12         //friend class Act;
 13     T data; 
 14     node< T > *lch;
 15     node< T > *rch;
 16     node();
 17     //node( const T &x );
 18     ~node();
 19 };
 20 
 21 template < typename T >
 22 class Act{
 23         public:
 24             void Init( node< T >* tr );
 25             void Print( node< T >* tr );
 26 };

//Tree.cpp
  1 #include<iostream>
  2 #include"Tree.h"
  3 using namespace std;
  4 template < typename T >
  5 void Act< T >::Init( node< T >* tr )
  6 {
  7     tr = new node< char >;
  8     cout << "输入data : " << flush;
  9     cin >> tr -> data;
 10     if ( tr -> data != "*" )
 11     {
 12             Init( tr -> lch );
 13             Init( tr -> rch );
 14     }       
 15 }   
 16 template < typename T >
 17 void Act< T >::Print(node< T >* tr )
 18 {
 19         if( tr -> data != "*" )
 20         {
 21                 cout << tr -> data << endl;
 22                 Print(tr -> lch ); 
 23                 Print(tr -> rch );
 24         }       
 25 }   

//Main.cpp
  1 #include<iostream>
  2 #include"Tree.h"
  3 using namespace std;
  4 int main()
  5 {
  6     node< char >* root;
  7     Act< char > act;
  8     act.Init( root );
  9     act.Print( root );
 10     
 11     return 0;
 12 }