Define geitonogamy.

Explanation

**Step-by-Step Solution:**

1. **Definition of Geitonogamy**: Geitonogamy is a type of self-fertilization in flowering plants.

2. **Mechanism of Geitonogamy**: In geitonogamy, pollen is transferred from one flower to another flower, but both flowers are on the same plant.

3. **Role of Vectors**: The transfer of pollen in geitonogamy is facilitated by vectors, which can include wind or pollinators (like bees or butterflies).

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