A closed collateral bundle is one where
(a) Xylem and phloem occur on different radii
(b) Collateral bundle occurs without cambium
(c) Xylem and phloem are separated by cambium
(d) Collateral bundle occurs with cambium

Options

A. Xylem and phloem occur on different radii
B. Collateral bundle occurs without cambium
C. Xylem and phloem are separated by cambium
D. Collateral bundle occurs with cambium

Answer

To solve the question regarding a closed collateral bundle, we need to analyze the options provided and understand the characteristics of closed collateral bundles.

### Step-by-Step Solution:

1. **Understanding Closed Collateral Bundles**:
- A closed collateral bundle is a type of vascular bundle where the xylem and phloem are located next to each other, but there is no cambium present between them.

2. **Analyzing the Options**:
- **Option (a)**: "Xylem and phloem occur on different radii" - This is incorrect for closed collateral bundles, as in these bundles, xylem and phloem are adjacent.
- **Option (b)**: "Collateral bundle occurs without cambium" - This is correct. Closed collateral bundles lack cambium, which means they cannot undergo secondary growth.
- **Option (c)**: "Xylem and phloem are separated by cambium" - This is incorrect. In closed collateral bundles, they are not separated by cambium.
- **Option (d)**: "Collateral bundle occurs with cambium" - This is also incorrect for closed collateral bundles, as they specifically do not have cambium.

3. **Conclusion**:
- The correct answer is **(b)**: "Collateral bundle occurs without cambium".

### Final Answer:
(b) Collateral bundle occurs without cambium.

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