How can you represent a Huffman-tree in Hex?
This practical problem comes up in JPEG, where you can define your own Huffman tables. The codewords are limited to 16 bits, and the table is stored as follows:

For $\ell=1,\ldots,16$, the number of codewords of length $\ell$ bits.
For each $\ell$, a list of the values encoded by the codewords of length $\ell$.

The codewords themselves need not be stored, since a Huffman code can be extracted from this description. See Imran Nazar's notes.