The permanently open structures seen on the bark of an old woody stem

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the structures that are permanently open on the bark of an old woody stem.

2. **Identifying the Structure**: In old woody stems, you can observe small dot-like or porous structures on the bark.

3. **Naming the Structure**: These structures are known as "lenticels."

4. **Function of Lenticels**: Lenticels play a crucial role in the plant's physiology. They facilitate gaseous exchange, allowing oxygen and carbon dioxide to diffuse in and out of the plant.

5. **Importance in Certain Plants**: In some plants where leaves are not present or are not effective for gas exchange, lenticels take on this important function.

6. **Conclusion**: Therefore, the answer to the question is "lenticels."