Algin is a phycocolloid, obtained from the cell wall of

Options

A. Macrocystis and Porphyridium
B. Mastigocladus and Laminaria
C. Microcystis and Nereocystis
D. Macrocystis and Fucus

Answer

To solve the question "Algin is a phycocolloid, obtained from the cell wall of," we need to analyze the options provided and understand the classification of algae.

### Step-by-Step Solution:

1. **Understand the Definition of Algin**:
- Algin is a phycocolloid, which is a gelatinous substance obtained from the cell walls of certain algae.

2. **Classify Algae**:
- Algae are classified into three major groups:
- **Chlorophyceae** (Green algae)
- **Rhodophyceae** (Red algae)
- **Phaeophyceae** (Brown algae)
- Additionally, there are cyanobacteria, also known as blue-green algae.

3. **Identify the Composition of Algal Cell Walls**:
- **Green Algae (Chlorophyceae)**: Cell walls primarily made of cellulose.
- **Red Algae (Rhodophyceae)**: Cell walls made of cellulose, pectin, and polysulfate esters.
- **Brown Algae (Phaeophyceae)**: Cell walls made of cellulose and algin.

4. **Analyze the Options**:
- The question provides several options: Microcystis, Porphyridium, Mastigocladus, Laminaria, Nereocystis, and Fucus.
- **Microcystis**: A cyanobacterium (not applicable).
- **Porphyridium**: A red algae (not applicable).
- **Mastigocladus**: A cyanobacterium (not applicable).
- **Laminaria**: A brown algae (contains algin).
- **Nereocystis**: A brown algae (contains algin).
- **Fucus**: A brown algae (contains algin).

5. **Conclusion**:
- Since algin is specifically found in the cell walls of brown algae, the correct options from the list are Laminaria, Nereocystis, and Fucus. However, the question asks for the specific answer among the provided options, which includes combinations.
- The correct answer is **Laminaria and Fucus**, as both are brown algae that contain algin.

### Final Answer:
Algin is a phycocolloid obtained from the cell wall of **Laminaria and Fucus**.