The prothallus of fern is

Options

A. Heart-shaped
B. Dorsiventral
C. Green
D. All of the above

Explanation

To answer the question "The prothallus of fern is:", we will analyze the characteristics of the prothallus and select the correct option based on the information provided.

### Step-by-Step Solution:

1. **Understanding Prothallus**: The prothallus is the gametophyte stage of ferns. It is a small, flat structure that is crucial in the life cycle of ferns.

2. **Shape of Prothallus**: The prothallus of ferns is typically described as heart-shaped. This distinctive shape is one of its identifying features.

3. **Dorsiventral Nature**: The prothallus is also dorsi-ventral, meaning it has two distinct surfaces: a top (dorsal) side and a bottom (ventral) side. This characteristic is important for its function and structure.

4. **Color of Prothallus**: The prothallus is green due to the presence of chlorophyll, which allows it to perform photosynthesis.

5. **Sex Organs**: On the lower surface of the prothallus, sex organs are present. These include archegonia (female) and antheridia (male), which are essential for reproduction.

6. **Conclusion**: Based on the characteristics discussed, the prothallus of ferns is heart-shaped, dorsi-ventral, and green. Therefore, the correct answer is option D: all of the above.

### Final Answer:
The prothallus of fern is heart-shaped, dorsi-ventral, green, and includes sex organs on its lower surface. Thus, the correct answer is option D: all of the above.

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