In which plant group reproductive organs are not enclosed in a layer of sterile cells?

Options

A. Pteridophyta
B. Thallophyta
C. Angiosperm
D. Gymnosperm

Answer

To answer the question "In which plant group are reproductive organs not enclosed in a layer of sterile cells?", we can analyze the options provided: Pteridophyta, Thallophyta, Angiosperms, and Gymnosperms.

### Step-by-Step Solution:

1. **Understanding Plant Groups**:
- **Thallophyta**: This group includes algae and is characterized by a thallus-like body structure. The reproductive organs in Thallophyta are typically non-jacketed, meaning they are not enclosed in a layer of sterile cells.
- **Bryophyta**: This group includes mosses and liverworts. In bryophytes, the reproductive organs (archegonia and antheridia) are covered by a layer of sterile cells, which is a significant distinction from Thallophyta.
- **Pteridophyta**: This group includes ferns. The reproductive organs in pteridophytes are also enclosed in a layer of sterile cells, similar to bryophytes.
- **Gymnosperms**: In gymnosperms, the reproductive structures (like cones) are also surrounded by sterile tissues, so they do not fit the criteria of being non-jacketed.
- **Angiosperms**: In angiosperms, the flowers contain reproductive organs that are enclosed within petals and sepals, which are also considered sterile structures.

2. **Identifying the Correct Group**:
- Based on the definitions and characteristics of each group, Thallophyta is the only group where the reproductive organs are not enclosed in a layer of sterile cells.

3. **Conclusion**:
- Therefore, the correct answer to the question is **Thallophyta**.

### Final Answer:
**Thallophyta** is the plant group in which reproductive organs are not enclosed in a layer of sterile cells.

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