Hogo de Vries gave his mutation theory on organic evolution while working on `:`

Options

A. Althea rosea
B. Drosophila melanogaster
C. Oenothera lamarckiana
D. Pisum sativum

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the organism on which Hugo de Vries conducted his research to develop his mutation theory of organic evolution.

2. **Identifying Hugo de Vries**: Hugo de Vries was a Dutch botanist known for his work in genetics and evolution. He is most famous for proposing the mutation theory, which suggests that new species arise from mutations in existing species.

3. **Reviewing the Options**: The options given are:
- Althea rosea
- Drosophila melanogaster
- Oenothera lamarckiana
- Pisum sativa

4. **Identifying the Correct Organism**:
- Hugo de Vries conducted his experiments primarily on **Oenothera lamarckiana**, commonly known as the evening primrose.
- His studies on this plant led him to propose that mutations could lead to the formation of new species, which is a key aspect of his mutation theory.

5. **Conclusion**: Therefore, the correct answer to the question is **Oenothera lamarckiana**.

**Final Answer**: Oenothera lamarckiana

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