Pollen has landed on a stigma. How does material from that pollen grain reach an ovule inside the ovary?

توضیح

The grain itself cannot move, and only the tube it grows can travel through the style: that pollen tube pushes down through the tissue beneath the stigma until it reaches an ovule, carrying a nucleus with it. Picturing the whole grain making the journey leaves it with no route to take, because the style is solid tissue rather than an open passage.