Please correct me if my understanding is incorrect; I understand branch/stem, and root are composed of different types of cells. Yet in some plants (e.g. rose, bougainvillea) a cutting from the stem is capable of developing and taking root.
How does this transformation from stem to root come about?
As an aside - I believe such root-generation happens only in plant cuttings, and not in a tree branch. Why? Is it a matter of the volume of nutrition required?