错误：无效使用非静态数据成员C ++

Question

list.hpp

template <typename Data>
class List{

   private:

     struct Node* Head;

   protected:

     using LinearContainer<Data>::size;

   struct Node
   {

      Data Elements;
      Node* Nxt;

      // Specific constructors
      Node(Data);

   };

   public:

   List() = default;
}

list.cpp

template<typename Data>
List<Data>::Node::Node(Data Elemento) {

    List<Data>::Head.Elements = Elemento;
    size = 1;
}

错误

error: invalid use of non-static data member 'Head'
    List<Data>::Head.Elements = Elemento;
    ~~~~~~~~~~~~^~~~
1 error generated.

我怎么了，你能告诉我吗？我还没有肯定地说过“ main”，因为“ size”是从更高的类继承而来的，与它无关。