Which of the following statements is correct ?

Options

A. Horsetails are gymnosperms
B. Selaginella is heterosporous, while Salvinia is homosporous
C. Ovules are not enclosed by ovary wall in gymnosperms
D. Stems are usually unbranched in both Cycas and Cedrus

Explanation

To solve the question "Which of the following statements is correct?", we will analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Analyze Statement A**: "Horsetails are gymnosperms."
- Horsetails belong to the group of plants known as pteridophytes, which are non-seed vascular plants. Gymnosperms are seed-producing plants. Therefore, this statement is **incorrect**.

2. **Analyze Statement B**: "Selaginella is heterosporous, Salvinia is homosporous."
- Both Selaginella and Salvinia are pteridophytes. Selaginella is indeed heterosporous (producing two types of spores), but Salvinia is also heterosporous, not homosporous. Thus, this statement is also **incorrect**.

3. **Analyze Statement C**: "Ovules are not enclosed by ovary wall in gymnosperms."
- In gymnosperms, ovules are indeed not enclosed by an ovary wall; they are exposed or "naked". This statement is **correct**.

4. **Analyze Statement D**: "Stems are unbranched in both Cycus and Sedrus."
- Cycas (Cycad) has branched stems, while Sedrus (Cedar) typically has unbranched stems. Therefore, this statement is **incorrect**.

### Conclusion:
Based on the analysis, the correct statement is **C**: "Ovules are not enclosed by ovary wall in gymnosperms."

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