Cells of two different filaments are involved in conjugation of Spirogyra. The type of sexual reproduction is

Options

A. Scalariform conjugation
B. Indirect lateral conjugation
C. Direct lateral conjugation
D. Terminal conjugation.

Answer

To solve the question regarding the type of sexual reproduction in Spirogyra involving cells of two different filaments during conjugation, follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: Recognize that Spirogyra is a green filamentous alga that reproduces sexually through a process called conjugation.

2. **Identify the Type of Conjugation**: The question specifies that cells from two different filaments are involved in the conjugation process.

3. **Recall the Types of Conjugation**: In Spirogyra, there are different types of conjugation:
- **Scleriform Conjugation**: Involves cells from two different filaments (heterothallic).
- **Lateral Conjugation**: Can be indirect or direct, and typically occurs within the same filament (homothallic).
- **Terminal Conjugation**: Not found in Spirogyra.

4. **Determine the Correct Answer**: Since the question specifies that the cells are from two different filaments, this indicates that the type of sexual reproduction occurring is **scleriform conjugation**.

5. **Conclusion**: Therefore, the correct answer to the question is **scleriform conjugation**.

### Final Answer:
The type of sexual reproduction in Spirogyra involving cells of two different filaments during conjugation is **scleriform conjugation**.