Which is not a lichen?

Options

A. Reindeer moss
B. Rock flowers
C. Stone mushroom
D. Puff balls

Answer

To determine which option is not a lichen, we will analyze each of the given options based on the definition of lichen and their characteristics.

### Step-by-Step Solution:

1. **Understanding Lichens**:
- Lichens are symbiotic associations between fungi and algae. The fungus can belong to either Ascomycetes or Basidiomycetes, while the algae can be green algae or blue-green algae (cyanobacteria).

2. **Analyzing the Options**:
- **Reindeer Moss**: Known as reindeer lichen, it is a type of lichen that is light-colored and fruticose. Therefore, this is a lichen.
- **Rock Flowers**: This is also a type of lichen that grows on trees, rocks, and stones and is used as a spice. Hence, this is a lichen.
- **Stone Mushroom**: This is another type of lichen that is used for food or medicinal purposes. Thus, this is also a lichen.
- **Puff Balls**: Puffballs are not lichens; they are a type of fungus belonging to the division Basidiomycota. They release spores when disturbed.

3. **Conclusion**:
- Among the options provided, the one that is not a lichen is **Puff Balls**.

### Final Answer:
**Puff Balls** are not a lichen.

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