The gametophyte is not an independent, free-living generation in

Options

A. Marchantia
B. Adiantum
C. Pinus
D. Polytrichum.

Answer

To answer the question "The gametophyte is not an independent, free-living generation in," we will analyze the options provided and identify which plant's gametophyte is dependent on the sporophyte.

### Step-by-Step Solution:

1. **Understanding Gametophyte and Sporophyte**:
- In the plant life cycle, there are two generations: the gametophyte (haploid) and the sporophyte (diploid). The gametophyte produces gametes, while the sporophyte produces spores.

2. **Identifying the Options**:
- The options given are Miltanthia, Adenatum, Pinus, and Polytrichum.

3. **Analyzing Each Option**:
- **Miltanthia**: This is a liverwort, which is a type of bryophyte. In liverworts, the gametophyte is the dominant generation, but it is dependent on the sporophyte for nutrition.
- **Adenatum**: This is also a type of plant where the gametophyte is not independent and relies on the sporophyte.
- **Pinus**: This is a gymnosperm. In Pinus, the sporophyte is the dominant generation, and the gametophyte is not independent; it is retained within the sporophyte structure (the cones).
- **Polytrichum**: This is a moss, and in mosses, the gametophyte is the dominant generation and is independent.

4. **Conclusion**:
- Among the options, both Miltanthia and Adenatum have dependent gametophytes, but Pinus is the most notable example where the gametophyte is not independent and is retained within the sporophyte. Therefore, the correct answer is **Pinus**.

### Final Answer:
The gametophyte is not an independent, free-living generation in **Pinus**.