'Olive tree' in the Bible

But if some of the branches were broken off, and you, being a wild olive, were grafted in among them, and became partaker with them of the root and of the richness of the olive tree;

For if you were cut out of that which is by nature a wild olive tree, and were grafted contrary to nature into a good olive tree, how much more will these, which are the natural branches, be grafted into their own olive tree?