I found a bug that happens with any non-intended case item (I tried it with the bookmark, photo, and key and it gives the same error):
>put clock in case
I place the clock into the Wardian case, but it has no effect.
[** Programming error: tried to read (something) **]
I place the clock into the Wardian case, but it has no effect. Perhaps the case's enchantment only works to transform plants into objects, while the reverse is impossible.