Extrastelar secondary growth takes place by :

Options

A. Vascular cambium
B. Phellogen
C. Phellem
D. Phelloderm

Answer

To solve the question about which tissue type is responsible for extrastellar secondary growth, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Extrastellar Secondary Growth**:
- Extrastellar secondary growth refers to the growth that occurs in the cortical region of a plant, specifically outside the stele (the central part of the stem that contains vascular tissues).

2. **Identify the Location of Extrastellar Growth**:
- This type of growth occurs in the tissues that are exterior to the stele, which includes the cortex and the outer layers of the stem.

3. **Recognize the Key Tissues Involved**:
- The main tissue responsible for extrastellar secondary growth is the cork cambium, also known as phallogen. This tissue is crucial for producing secondary growth in the outer regions of the plant.

4. **Differentiate Between Types of Cambium**:
- Vascular cambium is involved in the formation of secondary vascular tissues (xylem and phloem) and is part of primary growth, not extrastellar secondary growth.
- Cork cambium (phallogen) is responsible for producing cork (phallum) and secondary cortex (phalloderm), which are essential for extrastellar growth.

5. **Select the Correct Answer**:
- Based on the understanding of the tissues involved, the correct answer to the question is phallogen (cork cambium), as it is the tissue responsible for extrastellar secondary growth.

### Final Answer:
- The correct answer is **phallogen** (cork cambium).