When transfer of pollen grains from anther to stigma of different plants takes place, it is called geitonogamy/xenogamy.

Answer

To answer the question regarding the transfer of pollen grains from the anther to the stigma of different plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Pollination**: Pollination is the process where pollen grains are transferred from the anther (the male part of the flower) to the stigma (the female part of the flower).

2. **Identifying the Types of Pollination**:
- **Geitonogamy**: This term refers to the transfer of pollen grains from the anther to the stigma of different flowers but on the same plant.
- **Xenogamy**: This term refers to the transfer of pollen grains from the anther of one plant to the stigma of a different plant.

3. **Analyzing the Given Question**: The question specifically asks about the transfer of pollen grains from the anther to the stigma of different plants.

4. **Choosing the Correct Answer**: Since the pollen transfer is occurring between different plants, the correct term is **Xenogamy**. This type of pollination involves genetically different pollen grains being transferred to the stigma, which promotes genetic diversity.

5. **Conclusion**: Therefore, the answer to the question is **Xenogamy**.

### Final Answer:
The transfer of pollen grains from anther to stigma of different plants is called **Xenogamy**.

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