I'm not sure I follow your apple/tree analogy. But I would say that Christianity is true, and that therefore other truths, no matter what their source, would point in the same direction. So ideas (such as dying/rising gods) could potentially arise in paganism, yet still have some truth, and then be subsumed by Christianity.

I highly recommend GK Chesterton's book "The Everlasting Man", its a short read and still worthwhile even for atheists or those of other faiths as the author is brilliant.