When the pollen grains are not transferred from anthers to the stigma in flower due to the barrier or fence, it is referred or when some natural barrier exists between androecium and gynoecium to check self pollination, it is known as

Options

A. Heterostyly
B. Herkogamy
C. Dichogamy
D. Cleistogamy

Explanation

**Step-by-Step Solution:**

1. **Understanding Pollination**: Pollination is the transfer of pollen grains from the anthers (male part) to the stigma (female part) of a flower. This process can occur within the same flower (self-pollination) or between different flowers (cross-pollination).

2. **Identifying Barriers**: In some plants, there are natural barriers that prevent the transfer of pollen from the anthers to the stigma. These barriers can be physical structures or spatial arrangements that separate the male and female reproductive organs.

3. **Terminology**: The question refers to a specific term used when these barriers exist to prevent self-pollination. The term that describes this phenomenon is "hercogamy."

4. **Understanding Hercogamy**: Hercogamy is a condition where the spatial arrangement of male and female reproductive structures acts as a natural barrier, reducing the chances of self-pollination. This adaptation promotes cross-pollination, which can enhance genetic diversity.

5. **Eliminating Other Options**:
- **Heterostyly**: This refers to the presence of flowers with different styles to promote cross-pollination but does not specifically refer to barriers.
- **Dichogamy**: This is when male and female reproductive organs mature at different times, also avoiding self-pollination but not necessarily involving a physical barrier.
- **Cleistogamy**: This promotes self-pollination as flowers do not open, which is the opposite of what the question is asking.

6. **Conclusion**: Therefore, the correct answer to the question is "hercogamy," as it specifically refers to the natural barriers that prevent self-pollination.

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