'Olive tree' in the Bible

But if some of the branches were broken off, and thou, being a wild olive, wast grafted in among them, and didst become partaker with them of the root of the fatness of the olive tree;

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