alist and multiple values for one key

[ncauderan@hotmail.com (Norbert C.)]

Hi,

       I would lile to find the "good way" to retrieve multiple values
for a given key in an alist.

       But I didn't find a natural way to do it. For example :
(setq trees '((pine . cones) (pine . acorns) (oak . acorns) (maple .
seeds)))
==> ((pine . cones) (pine . acorns) (oak . acorns) (maple . seeds))
(assoc 'pine trees)
==> (pine . cones)

What I'd like is something that returns each value associated with
'pine.

Any thought ?

Thank you,

Norbert