'Olive tree' in the Bible

And if some of the branches be broken off, and thou, being a wild olive tree, wert graffed in among them, and with them partakest of the root and fatness of the olive tree;

And these Jews also will be grafted [back] in [to the olive tree] if they do not continue in their lack of faith [in Christ], because God is able to graft them back in again.

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