'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,

And they, if they do not go on without faith, will be united to the tree again, because God is able to put them in again.

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?