Geitonogamy refers to the transfer of pollen from the anther of one flower to the stigma of another flower on the same plant. Some plants are capable of this type of self-pollination, while others require cross-pollination from another plant.

Among the given options, the plant that does not undergo geitonogamy is the sweet potato. This is because sweet potatoes are propagated vegetatively, meaning that they are grown from cuttings or tubers rather than from seeds.

Explanation:

Vegetative propagation:
- Sweet potatoes are propagated vegetatively, meaning that new plants are grown from cuttings or tubers rather than from seeds.
- The cuttings can be taken from the stem or vine of the sweet potato plant and planted in soil.
- The tubers can also be planted directly into the soil to produce new plants.
- In this method, there is no involvement of flowers, anther or stigma, hence no geitonogamy occurs.

Other options:
- Mulberry: Mulberry flowers are either male or female, and cross-pollination between plants is required for fruit production.
- Coconut: Coconut palms are dioecious, meaning that individual plants produce only male or female flowers. Cross-pollination is required for fruit production.
- Maize: Maize is a monoecious plant, meaning that it produces both male and female flowers on the same plant. Cross-pollination can occur, but self-pollination can also occur through geitonogamy.

Geitonogamy is a type of f pollination in which the anther is pollinated through wind and fertilizes with the female gamete of the same plant. As per this question sweet potatoes not even undergo pollination.