Which of the following is not correct?

Options

A. The megaspore mother cell is differentiated from one of the cells of the nucellus.
B. The megaspore mother cell divides meiotically to form four megaspores.
C. One of the megaspores enclosed within the megasporangium develops into a multicellular female gametophyte.
D. The multicellular female gametophyte is not retained within the megasporangium

Answer

To determine which statement is not correct regarding the development of the female gametophyte in plants, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Megaspore Mother Cell**:
- The megaspore mother cell (MMC) is derived from one of the cells of the nucellus, which is the nutritive tissue of the ovule.
- This statement is correct since the MMC is indeed differentiated from the nucellus.

2. **Meiotic Division of the Megaspore Mother Cell**:
- The MMC undergoes meiosis to produce four megaspores.
- This statement is also correct, as this process is known as megasporogenesis.

3. **Development of the Female Gametophyte**:
- One of the megaspores develops into a multicellular female gametophyte (embryo sac) through a process called monosporic development.
- This statement is correct as well, as it accurately describes the development process.

4. **Retention of the Female Gametophyte**:
- The statement claims that the multicellular female gametophyte is not retained within the megasporangium.
- This statement is incorrect because the female gametophyte (embryo sac) is indeed retained within the megasporangium, where fertilization occurs.

### Conclusion:
The statement that is **not correct** is the fourth one: "The multicellular female gametophyte is not retained within the megasporangium."

### Final Answer:
**The incorrect statement is option number four.**

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