These two species grow together naturally in the wilds.  However, this particular combination occurred quite by accident in one of our collections in South Florida.  The Ophioglossum pendulum (Ribbon fern) was a gift from Musa Mushlim in Malacca, Malaysia. The O. pendulum was growing out of a Platycerium coronarium.  The owner gave a piece to Reggie Whitehead who brought it back to Miami, and mounted it in a tree fern basket.  Approximately one year after having the O. pendulum, a spore from an Asplenium nidus (Bird's nest fern) landed on the substrata and began growing.  

This plant was growing on a covered patio, but in time, the bird's nest got too large while it was growing upward, and the fronds on the ribbon fern were growing too long, and subsequently the entire arrangement had to be moved outside to a high oak tree.  The plants are watered daily by a drip system hidden in the oak tree.