Once pollen lands on the stigma, it forms a pollen down through the longof the pistil [the female reproductive part] into the flower's – which contains ovules. fill in the blank

1. Pollen tube

2. Style

3. Ovary

Explanation:

This process is describing the process of POLLINATION, which is the transfer of pollen grains from the anther of a male flower (androecium) to the stigma of the female flower (gymnoecium). After pollination i.e. the pollen has landed on the sticky stigma, the pollen grows out a tube called POLLEN TUBE.

The pollen tube extends through the STYLE of the female flower called PISTIL to the OVARY. The ovary is the reproductive part of the female flower that produces the ovules, which the sperm in the pollen is about to fertilize.