In "Dr. Heidegger's Experiment," what happens to the rose?

We are told that the rose is incredibly important to Dr.
Heidegger, as it was given to him by Sylvia Ward to be worn on their wedding day before
her unfortunate death. However, it is also vitally important to the short story, as
Hawthorne uses it symbolically to reinforce the message of this tale. When Dr. Heidegger
throws the rose into the water from the Fountain of Youth, it blooms once
more:

Soon,
however, a singular change began to be visible. The crushed and dried petals stirred,
and assumed a deepening tinge of crimson, as if the flower were reviving from a
deathlike slumber; the slender stalk and twigs of foliage became green; and there was
the rose of half a century, looking as fresh as when Sylvia Ward had first given it to
her lover.

Of course, this
symbolises the change that is about to occur in each of the guests as they drink the
Water of Youth, and it also indicates the reversal in their youth at the end. When it
does fade once more, intriguingly, Dr. Heidegger says about
it:

"I love it
as well thus, as in its dewy
freshness."

Clearly, Dr.
Heidegger is pointing towards the moral of this story - ageing brings its own benefits,
such as reflection and wisdom, which are just as important and valuable as the youth
that his guests are so eager to re-live and waste once more.