How does a adjectives palm leaf grow, say aloud conceivably a rose palm leaf? When a leaf grows from a small palm leaf to a...

When a leaf grows from a small palm leaf to a large palm leaf, does the growth (addition of new cellular material) purloin place at the margins(edges) or near the vein?
If it takes place at the vein, which is where the most undifferentiated cell exist, why does the margins of the leaf not crack from stretching?