Pollen tubes of lily pollen, colored scanning electron micrograph (SEM). Two pollen grains (brown) have sprouted pollen tubes (orange). A pollen tube is produced by a pollen grain when it lands on the pistil (female part) of a flower. The tube burrows through the pistil to the ovaries, carrying the male sex cells to them for fertilization. Magnification: x550 when printed 10cm high.