'Olive tree' in the Bible

And if certain ones of the branches were broken off, and you being a wild olive-tree are grafted in among them, and have become a partaker of the root of the fatness of the olive-tree;

For if you, having been cut off the olive tree which is wild by nature, and contrary to nature were grafted into the good olive tree: how much more shall these, who are the natural branches, be grafted into their own olive tree?