You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For consistency, answers should be in all lower cased letters.

Category: EUROPEAN VACATION 
Clue: While in Rome, it's possible to stand with one foot in each of these countries
italy & vatican city

Category: BOTANY 
Clue: Cryptogams are not plants with secret meanings, but plants such as ferns that don't bear these
seeds

Category: BIOLOGY 
Clue: In plants & invertebrates, this outermost layer of protection is usually just one cell thick

epidermis