In Casuarina fertilisation takes place through

Options

A. Mesogamy
B. Porogamy
C. Chalazogamy
D. Apogamy.

Answer

To determine how fertilization takes place in Casuarina, we need to analyze the different methods of pollen tube entry into the ovule. Here’s a step-by-step breakdown:

### Step-by-Step Solution:

1. **Understanding Fertilization in Plants**: Fertilization in flowering plants involves the transfer of pollen from the male reproductive part to the female reproductive part, leading to the formation of a zygote.

2. **Identifying the Routes of Pollen Tube Entry**: The pollen tube can enter the ovule through different routes:
- **Mesogamy**: Pollen tube enters through the integuments.
- **Porogamy**: Pollen tube enters through the micropyle.
- **Chalazogamy**: Pollen tube enters through the chalazal region.
- **Apogamy**: Development of sporophyte from gametophyte without fusion of gametes.

3. **Analyzing the Options**:
- **Mesogamy**: Common in plants like cucumber and pistachio. Not applicable to Casuarina.
- **Porogamy**: Common in most angiosperms, where the pollen tube enters through the micropyle. Not applicable to Casuarina.
- **Chalazogamy**: This is when the pollen tube enters through the chalazal tissue, which is specifically noted for Casuarina.
- **Apogamy**: This is not relevant to the fertilization process in Casuarina.

4. **Conclusion**: Based on the analysis, the correct method of fertilization in Casuarina is through **chalazogamy**.

### Final Answer:
In Casuarina, fertilization takes place through **chalazogamy**.

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