'Olive tree' in the Bible

But if some of the branches were broken off, and you, an olive-tree of the fields, were put in among them, and were given a part with them in the root by which the olive-tree is made fertile,

For if you were cut out of a field olive-tree, and against the natural use were united to a good olive-tree, how much more will these, the natural branches, be united again with the olive-tree which was theirs?