Trees

 I dunno, maybe I missed the part of my education where I was supposed to learn how plants grow. Leaves do all the work, or 99% of the work, of using sunshine to build new molecules, so all the growing should be at the ends of the branches where the leaves are, right?  But the big impressive part of the tree is the trunk, not the little branches and leaves. Now the tree gets water from its roots. The water gets piped up to the leaves because of capillary action and magic plant action (oxymoron, eh?), but how do our new molecules of plant get back down the branches to the trunk? Answer me that, Elmo.