Tulip anther. Light micrograph of a cross-section through the anther of a tulip bud (Tulipa sp.), showing a full anther sac with developing pollen grains (white). The pollen grains, or male sex cells, have been produced from the pollen mother cells. The inside of the anther wall produces a nutrient fluid to nourish the pollen mother cells. The split in the walls between the two pollen sacs (top left) will eventually liberate the pollen.