A flower is zygomorphic when

Options

A. Any transverse section divides it into two equal halves
B. Only one transverse section divides it into two equal halves
C. Every vertical section passing through its centre divides it into two equal halven.
D. Only one vertical section passing through its centre divides it into two equal halves .

Answer

To determine when a flower is zygomorphic, we need to understand the definition of zygomorphic flowers and analyze the provided options.

### Step-by-Step Solution:

1. **Understand the Term "Zygomorphic":**
- Zygomorphic flowers are also known as bilaterally symmetrical flowers. This means that they can be divided into two equal halves along a specific plane.

2. **Identify the Correct Plane of Symmetry:**
- For a flower to be classified as zygomorphic, it should be possible to divide it into two equal halves by only one specific vertical plane.

3. **Analyze the Options:**
- **Option A:** Any transverse section divides it into two equal halves.
- This is incorrect because zygomorphic flowers are not defined by transverse sections.
- **Option B:** Only one transverse section divides it into two equal halves.
- This is also incorrect for the same reason as option A.
- **Option C:** Every vertical section passing through its center divides it into two equal halves.
- This is incorrect because zygomorphic flowers are defined by only one specific vertical section, not every vertical section.
- **Option D:** Only one vertical section passing through its center divides it into two equal halves.
- This is correct as it aligns with the definition of zygomorphic flowers.

4. **Conclusion:**
- The correct answer is **Option D:** Only one vertical section passing through its center divides it into two equal halves.