bouquet
      |
      |    --------------       ---------------       ----------------
      |   | car   | cdr  |     | car    | cdr  |     | car     | cdr  |
       -->| rose  |   o------->| violet |   o------->| butter- |  nil |
          |       |      |     |        |      |     | cup     |      |
           --------------       ---------------       ----------------