|I heard the mother fern was bad incase your cat maybe took a bite out of it??
|A quick search of several databases of poisonous plants beginning with the Cornell University listing and related links
did not bring up any references to Asplenium bulbiferum or mother fern. However, this could simply mean there are just no cases reported.
In general, it is not a good idea to allow a cat to nibble on your houseplants (for both the plants and the cat), so perhaps you can cage the plants or keep them in a separate room if you have a cat who likes to eat them routinely. Some people have had success using a commerical repellent sprayed on the plants to train the cat to leave the plants alone.
If you have a concern about a cat eating something it shouild not have, it is usually a good idea to call the veterinarian right away and get an immediate answer in case emergency measures should be taken.