A more intense impression of what these metamorphoses actually mean is achieved by altering our mode of contemplation in the following way. After repeated and careful observation of the different forms on either of the plates, we build up inwardly, as a memory picture, the shape of the first leaf, and then transform this mental image successively into the images of the ensuing forms until we reach the final stage. The same process can also be tried retrogressively, and so repeated forward and backward.