On which plants did Darwin and Francis conduct their experiments ?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the specific plants that Charles Darwin and his son Francis used for their experiments. It's important to identify both the plants and the type of experiment they conducted.

2. **Identifying the Experiment**: Darwin and Francis conducted experiments related to phototropism. Phototropism is the growth of plants in response to light direction, where plants bend towards the light source.

3. **Recognizing the Plant Types**: The specific plants used in their experiments were Oat and Grass. These plants were chosen because of their coleoptiles, which are the protective sheath covering the emerging shoot in monocotyledonous plants.

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