Cycas pinus Coralloid root Vivipary Anabaena Nostoc Marsilea Usnea Oscillatoria Pneumatophore Eichhorina.
(iv) Heterocyst is found in ………………. .

Answer

To answer the question regarding where heterocysts are found, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Heterocysts**:
- Heterocysts are specialized cells found in certain types of cyanobacteria (blue-green algae). Their primary function is to fix atmospheric nitrogen, which is essential for plant growth.

2. **Identifying the Organisms Listed**:
- The question provides a list of organisms: Cycas, Pinus, Coralloid root, Vivipary, Anabaena, Nostoc, Marsilea, Usnea, Oscillatoria, Pneumatophore, and Eichhornia.

3. **Recognizing Nitrogen-Fixing Organisms**:
- Among the listed organisms, we need to identify which ones are known for nitrogen fixation. Anabaena and Nostoc are both cyanobacteria known for this ability.

4. **Determining the Presence of Heterocysts**:
- Heterocysts are specifically found in some cyanobacteria. Anabaena and Nostoc are both capable of forming heterocysts, but we need to identify the correct answer from the options provided.

5. **Selecting the Correct Answer**:
- From the list, Nostoc is a well-known cyanobacterium that contains heterocysts. Therefore, the correct answer to the question "Heterocyst is found in ………………. ." is Nostoc.

### Final Answer:
Heterocyst is found in **Nostoc**.

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