clipped from: www.sciencedaily.com 
"When you look at a healthy tropical plant, you think you're seeing just one organism, but each leaf can have dozens of fungal species growing inside, some of which may protect the plant by excluding pathogens," explains Sunshine Van Bael, post-doctoral fellow at the Smithsonian Tropical Research Institute. The fungi growing inside leaves without causing disease to the plant are called endophytes: endo-, inside, and –phyte, plant.
"Fungi in the leaves were not welcome in the leaf cutter ants' garden," concluded Van Bael.
Their work is published online in the Proceedings of the Royal Society B.