Name: The plant from which we obtain indigo blue.

Answer

**Step-by-Step Solution:**

1. **Identify the Plant**: The question asks for the name of the plant from which indigo blue dye is obtained. One such plant is *Calanthe veratrifolia*.

2. **Classification of the Plant**: *Calanthe veratrifolia* belongs to the orchid family. Orchids are known for their diverse species and some of them produce dyes.

3. **Chemical Composition**: The leaves of *Calanthe veratrifolia* contain a chemical compound known as glycoside.

4. **Process of Dye Extraction**: The glycoside present in the leaves undergoes hydrolysis. Hydrolysis is a chemical process that breaks down compounds by the addition of water.

5. **Formation of Indigo Blue**: Through hydrolysis, the glycoside yields a blue dye known as indigo blue.

6. **Conclusion**: Therefore, the plant from which we obtain indigo blue dye is *Calanthe veratrifolia*.

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