Scalariform conjugation of Spirogyra occurs in
(a) Monoecious species
(b) Dioecious species
(c) Usually in dioecious species and some times in monoecious
(d) Equally frequent in monoecious and dioecious species

Options

A. Monoecious species
B. Dioecious species
C. Usually in dioecious species and some times in monoecious
D. Equally frequent in monoecious and dioecious species.

Answer

To solve the question regarding the occurrence of scalariform conjugation in Spirogyra, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Organism**: Spirogyra is a filamentous green algae known for its unique reproductive processes, particularly conjugation.

2. **Identify the Types of Conjugation**: There are different types of conjugation in Spirogyra, with scalariform conjugation being one of the most common forms. The other form mentioned is lateral conjugation.

3. **Define Monoecious and Dioecious**:
- **Monoecious species**: These species have both male and female reproductive structures on the same individual.
- **Dioecious species**: These species have separate male and female individuals.

4. **Analyze Scalariform Conjugation**: Scalariform conjugation can occur in both monoecious and dioecious species of Spirogyra. This means that both types of species can participate in this form of reproduction.

5. **Evaluate the Options**:
- (a) Monoecious species: Incorrect, as scalariform conjugation is not exclusive to monoecious species.
- (b) Dioecious species: Incorrect, as scalariform conjugation is not exclusive to dioecious species.
- (c) Usually in dioecious species and sometimes in monoecious: Incorrect, as it occurs in both types equally.
- (d) Equally frequent in monoecious and dioecious species: Correct, as scalariform conjugation occurs in both types with equal frequency.

6. **Conclusion**: The correct answer is (d) Equally frequent in monoecious and dioecious species.

### Final Answer:
(d) Equally frequent in monoecious and dioecious species.