Circinate vernation in ferns refers to :

Options

A. uncoiling of new leaves from the base toward the apex
B. system of leaf gaps in the stems
C. arrangement of sori on the leaf surface
D. presence of adventitious roots on the rhizome

Explanation

### Step-by-Step Solution:

1. **Understanding Circinate Vernation**:
- Circinate vernation is a specific term used to describe the arrangement of new leaves (fronds) in ferns. It refers to the way these leaves emerge from the plant.

2. **Identifying the Process**:
- In circinate vernation, new fronds are tightly coiled when they first appear. This coiling is a protective mechanism that helps the delicate leaf structure to develop safely.

3. **Uncoiling Mechanism**:
- As the frond matures, it begins to uncoil or unfurl from the base towards the apex (the tip of the leaf). This gradual unrolling allows the leaf to expand and reach its full size.

4. **Correct Option**:
- Among the given options, the one that describes this process accurately is "uncoiling of new leaves from the base toward the apex." This is the definition of circinate vernation.

5. **Conclusion**:
- Therefore, the correct answer to the question is that circinate vernation in ferns refers to the uncoiling of new leaves from the base toward the apex.