In the flowers of many plant species, pollen sacs contain tiny granules (mostly smaller than 4 micrometers) called orbicules, or Ubisch bodies, along with the pollen. The orbicules are sometimes in close contact with the pollen grains and can be dispersed into the atmosphere when the pollen is released from the flower's anthers. Although their function in the plant remains unknown, orbicules may prove useful as phylogenetic markers, and recent studies suggest that they may play a role in allergic reactions associated with pollen.