There was a time when I knew the names of fungi
I attended lectures given by H.J. Hudson
and read the classic textbook
Ingold CT & Hudson HJ (1993) The Biology of Fungi.
Chapman & Hall, London.
I knew about gills and spores and mycorrhiza.
Now I have forgotten the detail
but I can still take pleasure
in the shapes, fragility and delicate colours.
It is - as MissM suggested - an example of transience.