Gemma for vegetative reproduction occurs in

Options

A. Funaria
B. Fern
C. Marchantia
D. Riccia.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the occurrence of gemma for vegetative reproduction in certain plant groups. We need to identify which of the given options is correct.

2. **Analyzing the Options**:
- **A. Fenaria**: In most species of Fenaria, the vegetative structure is protonema (either primary or secondary). While gemma may occur on protonemal branches in some species, it is not the primary vegetative structure.
- **B. Fern**: In ferns, the primary vegetative structure for reproduction is sporangia, which are structures that produce spores, not gemma.
- **C. Markentia**: This is a genus of liverworts where gemmae are the primary vegetative structures used for reproduction. All species of Markentia utilize gemma for vegetative reproduction.
- **D. Rickettsia**: In Rickettsia, the vegetative structure is a prostate thallus, which does not involve gemmae for reproduction.

3. **Conclusion**: Based on the analysis, the correct answer is **C. Markentia**, as gemma for vegetative reproduction occurs in this genus.

**Final Answer**: Gemma for vegetative reproduction occurs in **Markentia**.

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