  So now we have something that looks more like what we have seen with streams.  But with streams we had an unraveled form, and so we might wonder what the unraveled form of trees is.  To some extent, it would be the pictures that we have already seen.  In particular, one could take a tree as we have defined them and give a description of how one would construct the picture.  (The full construction would take forever, of course, but the same is true of our work on streams.)  Conversely, given a picture, one could set down a tree system for it, where a “tree system” is a system of equations as in equation (6). (In general, the tree system would be infinite, but if you find a regular structure in the picture, then the system could be finite.)