How to add, access, unset arrays in CI session?

[eluser]CodeIgniterNewbie[/eluser]
I want to add an array to CI session, then access it as an array (not individual elements of the array as I do not know exactly what the elements are), and later unset it. How do I do that? It seems like I can add arrays, but CI doesn't provide me with a way to access or unset arrays (of unknown elements).

Did I miss something?